Sample size. Medical search

The number of units (persons, animals, patients, specified circumstances, etc.) in a population to be studied. The sample size should be big enough to have a high likelihood of detecting a true difference between two groups. (From Wassertheil-Smoller, Biostatistics and Epidemiology, 1990, p95)

A plan for collecting and utilizing data so that desired information can be obtained with sufficient precision or so that an hypothesis can be tested properly.

Application of statistical procedures to analyze specific observed or assumed facts from a particular study.

Statistical formulations or analyses which, when applied to data and found to fit the data, are then used to verify the assumptions and parameters used in the analysis. Examples of statistical models are the linear model, binomial model, polynomial model, two-parameter model, etc.

Works about clinical trials that involve at least one test treatment and one control treatment, concurrent enrollment and follow-up of the test- and control-treated groups, and in which the treatments to be administered are selected by a random process, such as the use of a random-numbers table.

Computer-based representation of physical systems and phenomena such as chemical processes.

The probability distribution associated with two mutually exclusive outcomes; used to model cumulative incidence rates and prevalence rates. The Bernoulli distribution is a special case of binomial distribution.

Theoretical representations that simulate the behavior or activity of genetic processes or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.

The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.

Any deviation of results or inferences from the truth, or processes leading to such deviation. Bias can result from several sources: one-sided or systematic variations in measurement from the true value (systematic error); flaws in study design; deviation of inferences, interpretations, or analyses based on flawed data or data collection; etc. There is no sense of prejudice or subjectivity implied in the assessment of bias under these conditions.

Works about pre-planned studies of the safety, efficacy, or optimum dosage schedule (if appropriate) of one or more diagnostic, therapeutic, or prophylactic drugs, devices, or techniques selected according to predetermined criteria of eligibility and observed for predefined evidence of favorable and unfavorable effects. This concept includes clinical trials conducted both in the U.S. and in other countries.

A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.

A single nucleotide variation in a genetic sequence that occurs at appreciable frequency in the population.

Studies in which a number of subjects are selected from all subjects in a defined population. Conclusions based on sample results may be attributed only to the population sampled.

Evaluation undertaken to assess the results or consequences of management and procedures used in combating disease in order to determine the efficacy, effectiveness, safety, and practicability of these interventions in individual cases or series.

The form and structure of analytic studies in epidemiologic and clinical research.

A latent susceptibility to disease at the genetic level, which may be activated under certain conditions.

Studies which start with the identification of persons with a disease of interest and a control (comparison, referent) group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.

The genetic constitution of the individual, comprising the ALLELES present at each GENETIC LOCUS.

Small-scale tests of methods and procedures to be used on a larger scale if the pilot study demonstrates that these methods and procedures can work.

The science and art of collecting, summarizing, and analyzing data that are subject to random variation. The term is also applied to the data themselves and to the summarization of the data.

The application of STATISTICS to biological systems and organisms involving the retrieval or collection, analysis, reduction, and interpretation of qualitative and quantitative data.

The use of statistical and mathematical methods to analyze biological observations and phenomena.

A theorem in probability theory named for Thomas Bayes (1702-1761). In epidemiology, it is used to obtain the probability of disease in a group of people with some characteristic on the basis of the overall rate of that disease and of the likelihood of that characteristic in healthy and diseased individuals. The most familiar application is in clinical decision analysis where it is used for estimating the probability of a particular diagnosis given the appearance of some symptoms or test result.

The proportion of one particular in the total of all ALLELES for one genetic locus in a breeding POPULATION.

Functions constructed from a statistical model and a set of observed data which give the probability of that data for various values of the unknown model parameters. Those parameter values that maximize the probability are the maximum likelihood estimates of the parameters.

An analysis comparing the allele frequencies of all available (or a whole GENOME representative set of) polymorphic markers in unrelated patients with a specific symptom or disease condition, and those of healthy controls to identify markers associated with a specific disease or condition.

The study of chance processes or the relative frequency characterizing a chance process.

The complete summaries of the frequencies of the values or categories of a measurement made on a group of items, a population, or other collection of data. The distribution tells either how many or what proportion of the group was found to have each value (or each range of values) out of all the possible values that the quantitative measure can have.

In statistics, a technique for numerically approximating the solution of a mathematical problem by studying the distribution of some random variable, often generated by a computer. The name alludes to the randomness characteristic of the games of chance played at the gambling casinos in Monte Carlo. (From Random House Unabridged Dictionary, 2d ed, 1993)

Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.

The influence of study results on the chances of publication and the tendency of investigators, reviewers, and editors to submit or accept manuscripts for publication based on the direction or strength of the study findings. Publication bias has an impact on the interpretation of clinical trials and meta-analyses. Bias can be minimized by insistence by editors on high-quality research, thorough literature reviews, acknowledgement of conflicts of interest, modification of peer review practices, etc.

Works about studies that are usually controlled to assess the effectiveness and dosage (if appropriate) of diagnostic, therapeutic, or prophylactic drugs, devices, or techniques. These studies are performed on several hundred volunteers, including a limited number of patients with the target disease or disorder, and last about two years. This concept includes phase II studies conducted in both the U.S. and in other countries.

An aspect of personal behavior or lifestyle, environmental exposure, or inborn or inherited characteristic, which, on the basis of epidemiologic evidence, is known to be associated with a health-related condition considered important to prevent.

Nonrandom association of linked genes. This is the tendency of the alleles of two separate but already linked loci to be found together more frequently than would be expected by chance alone.

Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)

Establishment of the level of a quantifiable effect indicative of a biologic process. The evaluation is frequently to detect the degree of toxic or therapeutic effect.

The discipline studying genetic composition of populations and effects of factors such as GENETIC SELECTION, population size, MUTATION, migration, and GENETIC DRIFT on the frequencies of various GENOTYPES and PHENOTYPES using a variety of GENETIC TECHNIQUES.

Genotypic differences observed among individuals in a population.

Hybridization of a nucleic acid sample to a very large set of OLIGONUCLEOTIDE PROBES, which have been attached individually in columns and rows to a solid support, to determine a BASE SEQUENCE, or to detect variations in a gene sequence, GENE EXPRESSION, or for GENE MAPPING.

Statistical models in which the value of a parameter for a given value of a factor is assumed to be equal to a + bx, where a and b are constants. The models predict a linear regression.

The regular and simultaneous occurrence in a single interbreeding population of two or more discontinuous genotypes. The concept includes differences in genotypes ranging in size from a single nucleotide site (POLYMORPHISM, SINGLE NUCLEOTIDE) to large nucleotide sequences visible at a chromosomal level.

A quantitative method of combining the results of independent studies (usually drawn from the published literature) and synthesizing summaries and conclusions which may be used to evaluate therapeutic effectiveness, plan new studies, etc., with application chiefly in the areas of research and medicine.

Elements of limited time intervals, contributing to particular results or situations.

Factors that modify the effect of the putative causal factor(s) under study.

Positive test results in subjects who do not possess the attribute for which the test is conducted. The labeling of healthy persons as diseased when screening in the detection of disease. (Last, A Dictionary of Epidemiology, 2d ed)

The determination of the pattern of genes expressed at the level of GENETIC TRANSCRIPTION, under specific circumstances or in a specific cell.

A set of statistical methods used to group variables or observations into strongly inter-related subgroups. In epidemiology, it may be used to analyze a closely grouped series of events or cases of disease or other health-related phenomenon with well-defined distribution patterns in relation to time or place or both.

A range of values for a variable of interest, e.g., a rate, constructed so that this range has a specified probability of including the true value of the variable.

The analysis of a sequence such as a region of a chromosome, a haplotype, a gene, or an allele for its involvement in controlling the phenotype of a specific trait, metabolic pathway, or disease.

A phenotypically recognizable genetic trait which can be used to identify a genetic locus, a linkage group, or a recombination event.

A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.

The introduction of error due to systematic differences in the characteristics between those selected and those not selected for a given study. In sampling bias, error is the result of failure to ensure that all members of the reference population have a known chance of selection in the sample.

Those biological processes that are involved in the transmission of hereditary traits from one organism to another.

Sequential operating programs and data which instruct the functioning of a digital computer.

Computer-assisted interpretation and analysis of various mathematical functions related to a particular problem.

Research aimed at assessing the quality and effectiveness of health care as measured by the attainment of a specified end result or outcome. Measures include parameters such as improved health, lowered morbidity or mortality, and improvement of abnormal states (such as elevated blood pressure).

Precise and detailed plans for the study of a medical or biomedical problem and/or plans for a regimen of therapy.

The ratio of two odds. The exposure-odds ratio for case control data is the ratio of the odds in favor of exposure among cases to the odds in favor of exposure among noncases. The disease-odds ratio for a cohort or cross section is the ratio of the odds in favor of disease among the exposed to the odds in favor of disease among the unexposed. The prevalence-odds ratio refers to an odds ratio derived cross-sectionally from studies of prevalent cases.

Studies in which subsets of a defined population are identified. These groups may or may not be exposed to factors hypothesized to influence the probability of the occurrence of a particular disease or other outcome. Cohorts are defined populations which, as a whole, are followed in an attempt to determine distinguishing subgroup characteristics.

Procedures for finding the mathematical function which best describes the relationship between a dependent variable and one or more independent variables. In linear regression (see LINEAR MODELS) the relationship is constrained to be a straight line and LEAST-SQUARES ANALYSIS is used to determine the best fit. In logistic regression (see LOGISTIC MODELS) the dependent variable is qualitative rather than continuously variable and LIKELIHOOD FUNCTIONS are used to find the best relationship. In multiple regression, the dependent variable is considered to depend on more than a single independent variable.

A class of statistical methods applicable to a large set of probability distributions used to test for correlation, location, independence, etc. In most nonparametric statistical tests, the original scores or observations are replaced by another variable containing less information. An important class of nonparametric tests employs the ordinal properties of the data. Another class of tests uses information about whether an observation is above or below some fixed value such as the median, and a third class is based on the frequency of the occurrence of runs in the data. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1284; Corsini, Concise Encyclopedia of Psychology, 1987, p764-5)

The genetic constitution of individuals with respect to one member of a pair of allelic genes, or sets of genes that are closely linked and tend to be inherited together such as those of the MAJOR HISTOCOMPATIBILITY COMPLEX.

Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.

The co-inheritance of two or more non-allelic GENES due to their being located more or less closely on the same CHROMOSOME.

Predetermined sets of questions used to collect data - clinical data, social status, occupational group, etc. The term is often applied to a self-completed survey instrument.

Any method used for determining the location of and relative distances between genes on a chromosome.

The total number of cases of a given disease in a specified population at a designated time. It is differentiated from INCIDENCE, which refers to the number of new cases in the population at a given time.

New abnormal growth of tissue. Malignant neoplasms show a greater degree of anaplasia and have the properties of invasion and metastasis, compared to benign neoplasms.

Studies to determine the advantages or disadvantages, practicability, or capability of accomplishing a projected plan, study, or project.

A method of studying a drug or procedure in which both the subjects and investigators are kept unaware of who is actually getting which specific treatment.

Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.

The complete genetic complement contained in the DNA of a set of CHROMOSOMES in a HUMAN. The length of the human genome is about 3 billion base pairs.

A plant family of the order Pinales, class Pinopsida, division Coniferophyta, known for the various conifers.

Methods, procedures, and tests performed to diagnose disease, disordered function, or disability.

A publication issued at stated, more or less regular, intervals.

"The business or profession of the commercial production and issuance of literature" (Webster's 3d). It includes the publisher, publication processes, editing and editors. Production may be by conventional printing methods or by electronic publishing.

Works about controlled studies which are planned and carried out by several cooperating institutions to assess certain variables and outcomes in specific patient populations, for example, a multicenter study of congenital anomalies in children.

Studies in which variables relating to an individual or group of individuals are assessed over a period of time.

Works about clinical trials involving one or more test treatments, at least one control treatment, specified outcome measures for evaluating the studied intervention, and a bias-free method for assigning patients to the test treatment. The treatment may be drugs, devices, or procedures studied for diagnostic, therapeutic, or prophylactic effectiveness. Control measures include placebos, active medicines, no-treatment, dosage forms and regimens, historical comparisons, etc. When randomization using mathematical techniques, such as the use of a random numbers table, is employed to assign patients to test or control treatments, the trials are characterized as RANDOMIZED CONTROLLED TRIALS AS TOPIC.

Committees established to review interim data and efficacy outcomes in clinical trials. The findings of these committees are used in deciding whether a trial should be continued as designed, changed, or terminated. Government regulations regarding federally-funded research involving human subjects (the "Common Rule") require (45 CFR 46.111) that research ethics committees reviewing large-scale clinical trials monitor the data collected using a mechanism such as a data monitoring committee. FDA regulations (21 CFR 50.24) require that such committees be established to monitor studies conducted in emergency settings.

Criteria and standards used for the determination of the appropriateness of the inclusion of patients with specific conditions in proposed treatment plans and the criteria used for the inclusion of subjects in various clinical trials and other research protocols.

Earlier than planned termination of clinical trials.

Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.

Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.

Statistical models which describe the relationship between a qualitative dependent variable (that is, one which can take only certain discrete values, such as the presence or absence of a disease) and an independent variable. A common application is in epidemiology for estimating an individual's risk (probability of a disease) as a function of a given risk factor.

Diseases that are caused by genetic mutations present during embryo or fetal development, although they may be observed later in life. The mutations may be inherited from a parent's genome or they may be acquired in utero.

Studies in which the presence or absence of disease or other health-related variables are determined in each member of the study population or in a representative sample at one particular time. This contrasts with LONGITUDINAL STUDIES which are followed over a period of time.

Systematic gathering of data for a particular purpose from various sources, including questionnaires, interviews, observation, existing records, and electronic devices. The process is usually preliminary to statistical analysis of the data.

The nursing specialty that deals with the care of women throughout their pregnancy and childbirth and the care of their newborn children.

The family Odobenidae, suborder PINNIPEDIA, order CARNIVORA. It is represented by a single species of large, nearly hairless mammal found on Arctic shorelines, whose upper canines are modified into tusks.

The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.

Levels within a diagnostic group which are established by various measurement criteria applied to the seriousness of a patient's disorder.

Genetic loci associated with a QUANTITATIVE TRAIT.

A field of biology concerned with the development of techniques for the collection and manipulation of biological data, and the use of such data to make biological discoveries or predictions. This field encompasses all computational methods and theories for solving biological problems including manipulation of models and datasets.

The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.

A system for verifying and maintaining a desired level of quality in a product or process by careful planning, use of proper equipment, continued inspection, and corrective action as required. (Random House Unabridged Dictionary, 2d ed)

The probability that an event will occur. It encompasses a variety of measures of the probability of a generally unfavorable outcome.

The qualitative or quantitative estimation of the likelihood of adverse effects that may result from exposure to specified health hazards or from the absence of beneficial influences. (Last, Dictionary of Epidemiology, 1988)

Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.

Extensive collections, reputedly complete, of facts and data garnered from material of a specialized subject area and made available for analysis and application. The collection can be automated by various contemporary methods for retrieval. The concept should be differentiated from DATABASES, BIBLIOGRAPHIC which is restricted to collections of bibliographic references.

An infant during the first month after birth.

A formal process of examination of patient care or research proposals for conformity with ethical standards. The review is usually conducted by an organized clinical or research ethics committee (CLINICAL ETHICS COMMITTEES or RESEARCH ETHICS COMMITTEES), sometimes by a subset of such a committee, an ad hoc group, or an individual ethicist (ETHICISTS).

Individuals whose ancestral origins are in the southeastern and eastern areas of the Asian continent.

Research techniques that focus on study designs and data gathering methods in human and animal populations.

A statistical analytic technique used with discrete dependent variables, concerned with separating sets of observed values and allocating new values. It is sometimes used instead of regression analysis.

Individuals whose ancestral origins are in the continent of Europe.

Age as a constituent element or influence contributing to the production of a result. It may be applicable to the cause or the effect of a circumstance. It is used with human or animal concepts but should be differentiated from AGING, a physiological process, and TIME FACTORS which refers only to the passage of time.

The presence of apparently similar characters for which the genetic evidence indicates that different genes or different genetic mechanisms are involved in different pedigrees. In clinical settings genetic heterogeneity refers to the presence of a variety of genetic defects which cause the same disease, often due to mutations at different loci on the same gene, a finding common to many human diseases including ALZHEIMER DISEASE; CYSTIC FIBROSIS; LIPOPROTEIN LIPASE DEFICIENCY, FAMILIAL; and POLYCYSTIC KIDNEY DISEASES. (Rieger, et al., Glossary of Genetics: Classical and Molecular, 5th ed; Segen, Dictionary of Modern Medicine, 1992)

Research that involves the application of the natural sciences, especially biology and physiology, to medicine.

An approach of practicing medicine with the goal to improve and evaluate patient care. It requires the judicious integration of best research evidence with the patient's values to make decisions about medical care. This method is to help physicians make proper diagnosis, devise best testing plan, choose best treatment and methods of disease prevention, as well as develop guidelines for large groups of patients with the same disease. (from JAMA 296 (9), 2006)

A subdiscipline of human genetics which entails the reliable prediction of certain human disorders as a function of the lineage and/or genetic makeup of an individual or of any two parents or potential parents.

A generic concept reflecting concern with the modification and enhancement of life attributes, e.g., physical, political, moral and social environment; the overall condition of a human life.

Works about studies performed to evaluate the safety of diagnostic, therapeutic, or prophylactic drugs, devices, or techniques in healthy subjects and to determine the safe dosage range (if appropriate). These tests also are used to determine pharmacologic and pharmacokinetic properties (toxicity, metabolism, absorption, elimination, and preferred route of administration). They involve a small number of persons and usually last about 1 year. This concept includes phase I studies conducted both in the U.S. and in other countries.

A distribution function used to describe the occurrence of rare events or to describe the sampling distribution of isolated counts in a continuum of time or space.

A prediction of the probable outcome of a disease based on a individual's condition and the usual course of the disease as seen in similar situations.

A quantitative measure of the frequency on average with which articles in a journal have been cited in a given period of time.

Works about comparative studies to verify the effectiveness of diagnostic, therapeutic, or prophylactic drugs, devices, or techniques determined in phase II studies. During these trials, patients are monitored closely by physicians to identify any adverse reactions from long-term use. These studies are performed on groups of patients large enough to identify clinically significant responses and usually last about three years. This concept includes phase III studies conducted in both the U.S. and in other countries.

The significance of non-significance. (1/2102)

We discuss the implications of empirical results that are statistically non-significant. Figures illustrate the interrelations among effect size, sample sizes and their dispersion, and the power of the experiment. All calculations (detailed in Appendix) are based on actual noncentral t-distributions, with no simplifying mathematical or statistical assumptions, and the contribution of each tail is determined separately. We emphasize the importance of reporting, wherever possible, the a priori power of a study so that the reader can see what the chances were of rejecting a null hypothesis that was false. As a practical alternative, we propose that non-significant inference be qualified by an estimate of the sample size that would be required in a subsequent experiment in order to attain an acceptable level of power under the assumption that the observed effect size in the sample is the same as the true effect size in the population; appropriate plots are provided for a power of 0.8. We also point out that successive outcomes of independent experiments each of which may not be statistically significant on its own, can be easily combined to give an overall p value that often turns out to be significant. And finally, in the event that the p value is high and the power sufficient, a non-significant result may stand and be published as such. (+info)

A simulation study of confounding in generalized linear models for air pollution epidemiology. (2/2102)

Confounding between the model covariates and causal variables (which may or may not be included as model covariates) is a well-known problem in regression models used in air pollution epidemiology. This problem is usually acknowledged but hardly ever investigated, especially in the context of generalized linear models. Using synthetic data sets, the present study shows how model overfit, underfit, and misfit in the presence of correlated causal variables in a Poisson regression model affect the estimated coefficients of the covariates and their confidence levels. The study also shows how this effect changes with the ranges of the covariates and the sample size. There is qualitative agreement between these study results and the corresponding expressions in the large-sample limit for the ordinary linear models. Confounding of covariates in an overfitted model (with covariates encompassing more than just the causal variables) does not bias the estimated coefficients but reduces their significance. The effect of model underfit (with some causal variables excluded as covariates) or misfit (with covariates encompassing only noncausal variables), on the other hand, leads to not only erroneous estimated coefficients, but a misguided confidence, represented by large t-values, that the estimated coefficients are significant. The results of this study indicate that models which use only one or two air quality variables, such as particulate matter [less than and equal to] 10 microm and sulfur dioxide, are probably unreliable, and that models containing several correlated and toxic or potentially toxic air quality variables should also be investigated in order to minimize the situation of model underfit or misfit. (+info)

Laboratory assay reproducibility of serum estrogens in umbilical cord blood samples. (3/2102)

We evaluated the reproducibility of laboratory assays for umbilical cord blood estrogen levels and its implications on sample size estimation. Specifically, we examined correlation between duplicate measurements of the same blood samples and estimated the relative contribution of variability due to study subject and assay batch to the overall variation in measured hormone levels. Cord blood was collected from a total of 25 female babies (15 Caucasian and 10 Chinese-American) from full-term deliveries at two study sites between March and December 1997. Two serum aliquots per blood sample were assayed, either at the same time or 4 months apart, for estrone, total estradiol, weakly bound estradiol, and sex hormone-binding globulin (SHBG). Correlation coefficients (Pearson's r) between duplicate measurements were calculated. We also estimated the components of variance for each hormone or protein associated with variation among subjects and variation between assay batches. Pearson's correlation coefficients were >0.90 for all of the compounds except for total estradiol when all of the subjects were included. The intraclass correlation coefficient, defined as a proportion of the total variance due to between-subject variation, for estrone, total estradiol, weakly bound estradiol, and SHBG were 92, 80, 85, and 97%, respectively. The magnitude of measurement error found in this study would increase the sample size required for detecting a difference between two populations for total estradiol and SHBG by 25 and 3%, respectively. (+info)

A note on power approximations for the transmission/disequilibrium test. (4/2102)

The transmission/disequilibrium test (TDT) is a popular method for detection of the genetic basis of a disease. Investigators planning such studies require computation of sample size and power, allowing for a general genetic model. Here, a rigorous method is presented for obtaining the power approximations of the TDT for samples consisting of families with either a single affected child or affected sib pairs. Power calculations based on simulation show that these approximations are quite precise. By this method, it is also shown that a previously published power approximation of the TDT is erroneous. (+info)

Comparison of linkage-disequilibrium methods for localization of genes influencing quantitative traits in humans. (5/2102)

Linkage disequilibrium has been used to help in the identification of genes predisposing to certain qualitative diseases. Although several linkage-disequilibrium tests have been developed for localization of genes influencing quantitative traits, these tests have not been thoroughly compared with one another. In this report we compare, under a variety of conditions, several different linkage-disequilibrium tests for identification of loci affecting quantitative traits. These tests use either single individuals or parent-child trios. When we compared tests with equal samples, we found that the truncated measured allele (TMA) test was the most powerful. The trait allele frequencies, the stringency of sample ascertainment, the number of marker alleles, and the linked genetic variance affected the power, but the presence of polygenes did not. When there were more than two trait alleles at a locus in the population, power to detect disequilibrium was greatly diminished. The presence of unlinked disequilibrium (D'*) increased the false-positive error rates of disequilibrium tests involving single individuals but did not affect the error rates of tests using family trios. The increase in error rates was affected by the stringency of selection, the trait allele frequency, and the linked genetic variance but not by polygenic factors. In an equilibrium population, the TMA test is most powerful, but, when adjusted for the presence of admixture, Allison test 3 becomes the most powerful whenever D'*>.15. (+info)

Measurement of continuous ambulatory peritoneal dialysis prescription adherence using a novel approach. (6/2102)

OBJECTIVE: The purpose of the study was to test a novel approach to monitoring the adherence of continuous ambulatory peritoneal dialysis (CAPD) patients to their dialysis prescription. DESIGN: A descriptive observational study was done in which exchange behaviors were monitored over a 2-week period of time. SETTING: Patients were recruited from an outpatient dialysis center. PARTICIPANTS: A convenience sample of patients undergoing CAPD at Piedmont Dialysis Center in Winston-Salem, North Carolina was recruited for the study. Of 31 CAPD patients, 20 (64.5%) agreed to participate. MEASURES: Adherence of CAPD patients to their dialysis prescription was monitored using daily logs and an electronic monitoring device (the Medication Event Monitoring System, or MEMS; APREX, Menlo Park, California, U.S.A.). Patients recorded in their logs their exchange activities during the 2-week observation period. Concurrently, patients were instructed to deposit the pull tab from their dialysate bag into a MEMS bottle immediately after performing each exchange. The MEMS bottle was closed with a cap containing a computer chip that recorded the date and time each time the bottle was opened. RESULTS: One individual's MEMS device malfunctioned and thus the data presented in this report are based upon the remaining 19 patients. A significant discrepancy was found between log data and MEMS data, with MEMS data indicating a greater number and percentage of missed exchanges. MEMS data indicated that some patients concentrated their exchange activities during the day, with shortened dwell times between exchanges. Three indices were developed for this study: a measure of the average time spent in noncompliance, and indices of consistency in the timing of exchanges within and between days. Patients who were defined as consistent had lower scores on the noncompliance index compared to patients defined as inconsistent (p = 0.015). CONCLUSIONS: This study describes a methodology that may be useful in assessing adherence to the peritoneal dialysis regimen. Of particular significance is the ability to assess the timing of exchanges over the course of a day. Clinical implications are limited due to issues of data reliability and validity, the short-term nature of the study, the small sample, and the fact that clinical outcomes were not considered in this methodology study. Additional research is needed to further develop this data-collection approach. (+info)

Statistical power of MRI monitored trials in multiple sclerosis: new data and comparison with previous results. (7/2102)

OBJECTIVES: To evaluate the durations of the follow up and the reference population sizes needed to achieve optimal and stable statistical powers for two period cross over and parallel group design clinical trials in multiple sclerosis, when using the numbers of new enhancing lesions and the numbers of active scans as end point variables. METHODS: The statistical power was calculated by means of computer simulations performed using MRI data obtained from 65 untreated relapsing-remitting or secondary progressive patients who were scanned monthly for 9 months. The statistical power was calculated for follow up durations of 2, 3, 6, and 9 months and for sample sizes of 40-100 patients for parallel group and of 20-80 patients for two period cross over design studies. The stability of the estimated powers was evaluated by applying the same procedure on random subsets of the original data. RESULTS: When using the number of new enhancing lesions as the end point, the statistical power increased for all the simulated treatment effects with the duration of the follow up until 3 months for the parallel group design and until 6 months for the two period cross over design. Using the number of active scans as the end point, the statistical power steadily increased until 6 months for the parallel group design and until 9 months for the two period cross over design. The power estimates in the present sample and the comparisons of these results with those obtained by previous studies with smaller patient cohorts suggest that statistical power is significantly overestimated when the size of the reference data set decreases for parallel group design studies or the duration of the follow up decreases for two period cross over studies. CONCLUSIONS: These results should be used to determine the duration of the follow up and the sample size needed when planning MRI monitored clinical trials in multiple sclerosis. (+info)

Power and sample size calculations in case-control studies of gene-environment interactions: comments on different approaches. (8/2102)

Power and sample size considerations are critical for the design of epidemiologic studies of gene-environment interactions. Hwang et al. (Am J Epidemiol 1994;140:1029-37) and Foppa and Spiegelman (Am J Epidemiol 1997;146:596-604) have presented power and sample size calculations for case-control studies of gene-environment interactions. Comparisons of calculations using these approaches and an approach for general multivariate regression models for the odds ratio previously published by Lubin and Gail (Am J Epidemiol 1990; 131:552-66) have revealed substantial differences under some scenarios. These differences are the result of a highly restrictive characterization of the null hypothesis in Hwang et al. and Foppa and Spiegelman, which results in an underestimation of sample size and overestimation of power for the test of a gene-environment interaction. A computer program to perform sample size and power calculations to detect additive or multiplicative models of gene-environment interactions using the Lubin and Gail approach will be available free of charge in the near future from the National Cancer Institute. (+info)

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Consensus-Based Sample Size Version 1.0, July 2019. Four sets of R functions for calculating sample size requirements to ensure ... Bayesian Sample Size. See related papers. Change-point methods and applications. Diagnostic testing. Diagnostic testing in ... Bayesian Sample Size Determination for Prevalence and Diagnostic Test Studies in the Absence of a Gold Standard Test. Nandini ... Bayesian Sample Size Criteria for Linear and Logistic Regression in the Presence of Confounding and Measurement Error Version ...

https://www.medicine.mcgill.ca/epidemiology/Joseph/software/Bayesian-Sample-Size.html

Student sample sizes and target populations in NAEP mathematics at grade 4, by district: 2009 District. Sample size. Target ... NOTE: The sample size is rounded to the nearest hundred. The target population is rounded to the nearest thousand. DCPS = ... More information on sampling can be found in NAEP Technical Documentation.. The sample of students in the participating Trial ... About the Assessment: Target Population and Sample Size. The schools and students participating in NAEP assessments are ...

https://www.nationsreportcard.gov/math_2009/target_pop.aspx?subtab_id=Tab_1&tab_id=tab2

Constructing small sample size confidence intervals using t-distributions ... And in particular, this is going to be a particularly bad estimate when we have a small sample size, a size less than 30. So ... So if you take a random sample, and thats exactly what we did when we found these 7 samples. When we took these 7 samples and ... and your sample size is small, and youre going to use this to estimate the standard deviation of your sampling distribution, ...

https://www.khanacademy.org/math/statistics-probability/confidence-intervals-one-sample/old-confidence-interval-videos/v/small-sample-size-confidence-intervals

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This free sample size calculator determines the sample size required to meet a given set of constraints. Also, learn more about ... sample size calculator. Sample Size Calculator. Find Out The Sample Size. This calculator computes the minimum number of ... Sample Size Calculation. Sample size is a statistical concept that involves determining the number of observations or ... of the random samples that could be taken. The confidence interval depends on the sample size, n (the variance of the sample ...

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Determining the Correct Sample Size when AQL points to two Sample Sizes. AQL - Acceptable Quality Level. 7. May 28, 2012. ... Surveillance Sampling Test - Determining Sample Size. Inspection, Prints (Drawings), Testing, Sampling and Related Topics. 5. ... Determining the Correct Sample Size when AQL points to two Sample Sizes *Started by Hiccup ... Functional Test Sampling - Determining Sample Size to eliminate 100% Testing. Inspection, Prints (Drawings), Testing, Sampling ...

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Reducing Sample Sizes in the National Compensation Survey in Response to Budget Cuts ... There are 3 phases of sampling: localities, establishments, and jobs. The establishment-sample has 2 parts: a "wage sample" for ... all reductions were designed to preserve Index sample sizes, and most reductions involved subsamples of "wage-only" samples ( ... Reducing Sample Sizes in the National Compensation Survey in Response to Budget Cuts. Christopher J. Guciardo, Lawrence R. ...

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a calculation known as "sample size calculation. (calculator.net)
Sample size calculation is very important in statistical inference and findings. (statisticssolutions.com)
Sample size calculation ascertains the correct sample size that would represent the population as a whole. (statisticssolutions.com)
Sample size calculation for different statistical testing varies depending on the formulae used. (statisticssolutions.com)
Sample size calculation cannot be performed with only one method or technique. (statisticssolutions.com)
Sample size calculation is legitimate for most relevant tests, like the t test , z test, f test, etc. (statisticssolutions.com)
Sample size calculation depends on the different statistical tests that are to be carried out, because with a change in statistical tests, the results are also dissimilar. (statisticssolutions.com)
Depending on the size of the population or the accuracy of the result, the size of the sample in sample size calculation varies. (statisticssolutions.com)
Sample size calculation depends on many factors that are more commonly known as qualitative factors. (statisticssolutions.com)
These are important to help calculate any kind of sample size calculation and determination. (statisticssolutions.com)
In qualitative research , the sample size in sample size calculation is usually small. (statisticssolutions.com)
Sample size calculation in biomedical practice is typically based on the problematic Wald method for a binomial proportion, with potentially dangerous consequences. (mdpi.com)
Background A common approach to sample size calculation for cluster randomised trials (CRTs) is to calculate the sample size assuming individual randomisation and multiply it by an inflation factor, the design effect. (bl.uk)
I provide practical guidance for sample size calculation for ordinal outcomes in CRTs. (bl.uk)
This assumption severely compromises one's ability to compute required sample sizes for high-powered indirect standardization , as in contexts where sample size calculation is desired, there are usually no means of knowing this distribution. (bvsalud.org)
This paper presents novel statistical methodology to perform sample size calculation for the standardized incidence ratio without knowing the covariate distribution of the index hospital and without collecting information from the index hospital to estimate this covariate distribution. (bvsalud.org)

And then you can also calculate your sample standard deviation. (khanacademy.org)
However, sampling statistics can be used to calculate what are called confidence intervals, which are an indication of how close the estimate p̂ is to the true value p . (calculator.net)
Information on model parameters and sampling costs are required to calculate these optimal sample sizes. (maastrichtuniversity.nl)

Sampling and engine after-treatment effect on diesel exhaust particle size distributions is studied by reviewing measurement data from a heavy-duty diesel engine and from a diesel aggregate. (sae.org)
Measured data was evaluated for nucleation effects on particle size distributions. (sae.org)
Transformation of size distributions through coagulation is calculated in standard diesel sampling systems and in the Fine Particle Sampler (FPS). (sae.org)
Sampling and Engine After-Treatment Effect On Diesel Exhaust Particle Size Distributions," SAE Technical Paper 2005-01-0192, 2005, https://doi.org/10.4271/2005-01-0192 . (sae.org)
As sample sizes increase, the sampling distributions approach a normal distribution. (thelittleaussiebakery.com)
We present a novel two-stage, stopped-flow, continuous centrifugal sedimentation strategy to measure the size distributions of events (defined here as cells or clusters thereof) in a blood sample. (nature.com)

An estimation of the sampled depth was made. (archives-ouvertes.fr)
Along with the estimation of the sampled volume, the evolution of the SNR (signal to noise ratio) as a function of the laser energy was investigated as well. (archives-ouvertes.fr)
Estimation of Li-Ion Degradation Test Sample Sizes Required to Understand Cell-to-Cell Variabili. (rwth-aachen.de)
Item Response Theory (IRT) has been considered an important development for the modern psychometrics because of its several advantages compared to Classic Test Theory (CTT), such as: the virtual invariance of item parameters in respect to the sample used in their estimation, more reliable and interpretable identification of person`s ability and more efficient procedures for test equating. (bvsalud.org)

So the whole focus of this video is when we think about the sampling distribution, which is what we're going to use to generate our interval, instead of assuming that the sampling distribution is normal like we did in many other videos using the central limit theorem and all of that, we're going to tweak the sampling distribution. (khanacademy.org)
For an explanation of why the sample estimate is normally distributed, study the Central Limit Theorem . (calculator.net)
The central limit theorem states that the sampling distribution of the mean approaches a normal distribution, as the sample size increases. (thelittleaussiebakery.com)

PASS provides sample size calculations for over 370 more scenarios than any other sample size software and is the premier software tool for determining the needed sample size or analyzing the power of a study. (ncss.com)
The confidence interval calculations assume you have a genuine random sample of the relevant population. (surveysystem.com)
Sample size calculations for indirect standardization. (bvsalud.org)

Droplet size measurements obtained by sampling at discrete spray plume locations were compared to those obtained by sweeping the spray plume from fan nozzles through the sampling area of a laser droplet imaging probe. (astm.org)
This sample demonstrates how to visualize 2D point features based on real-world sizes or measurements. (arcgis.com)
Less-frequent measurements lead to a bias in the effect size towards zero, especially if disease is rare. (who.int)

Four sets of R functions for calculating sample size requirements to ensure posterior agreement from different priors using a variety of Bayesian criteria. (mcgill.ca)

A set of R functions for calculating sample size requirements using three different Bayesian criteria in the context of designing an experiment to estimate a normal mean or the difference between two normal means. (mcgill.ca)
And a t-distribution is essentially, the best way to think about is it's almost engineered so it gives a better estimate of your confidence intervals and all of that when you do have a small sample size. (khanacademy.org)
So normally what we do is we find the estimate of the true standard deviation, and then we say that the standard deviation of the sampling distribution is equal to the true standard deviation of our population divided by the square root of n. (khanacademy.org)
And in particular, this is going to be a particularly bad estimate when we have a small sample size, a size less than 30. (khanacademy.org)
So when you are estimating the standard deviation where you don't know it, you're estimating it with your sample standard deviation, and your sample size is small, and you're going to use this to estimate the standard deviation of your sampling distribution, you don't assume your sampling distribution is a normal distribution. (khanacademy.org)
Thus, to estimate p in the population, a sample of n individuals could be taken from the population, and the sample proportion, p̂ , calculated for sampled individuals who have brown hair. (calculator.net)
Unfortunately, unless the full population is sampled, the estimate p̂ most likely won't equal the true value p , since p̂ suffers from sampling noise, i.e. it depends on the particular individuals that were sampled. (calculator.net)
The uncertainty in a given random sample (namely that is expected that the proportion estimate, p̂ , is a good, but not perfect, approximation for the true proportion p ) can be summarized by saying that the estimate p̂ is normally distributed with mean p and variance p(1-p)/n . (calculator.net)
The confidence level gives just how "likely" this is - e.g., a 95% confidence level indicates that it is expected that an estimate p̂ lies in the confidence interval for 95% of the random samples that could be taken. (calculator.net)
This practice is intended for use in determining the sample size required to estimate, with specified precision, a measure of quality of a lot or process. (astm.org)
This practice is intended for use in determining the sample size required to estimate, with specified precision, such a measure of the quality of a lot or process either as an average value or as a fraction not conforming to a specified value. (astm.org)
1.1 This practice covers simple methods for calculating how many units to include in a random sample in order to estimate with a specified precision, a measure of quality for all the units of a lot of material, or produced by a process. (astm.org)
This practice will clearly indicate the sample size required to estimate the average value of some property or the fraction of nonconforming items produced by a production process during the time interval covered by the random sample. (astm.org)
This vignette provides an overview of the primary function of the phylosamp package: how to estimate the false discovery rate given a sample size. (fhcrc.org)
As our sample size increases, the confidence in our estimate increases, our uncertainty decreases and we have greater precision. (thelittleaussiebakery.com)
The strength and the direction of the effect size estimate for total stroke, IS, ICH, and SAH remained stable for most subgroups. (medscape.com)

The Kaiser Family Foundation/Episcopal Health Foundation Texas Health Policy Survey was conducted by telephone March 28 - May 8, 2018 among a random representative sample of 1,367 adults age 18 and older living in the state of Texas (note: persons without a telephone could not be included in the random selection process). (kff.org)

Repeat samples from bears were counted individually if bears were sampled between periods. (cdc.gov)
We found that median concentrations for PM1 (particle size ≤ 1 µm) and PM10 (particle size ≤ 10 µm) were highest when trucks passed by at sampling locations, followed by periods when trains passed by. (cdc.gov)

The Blood Analysis Sampling Tube Market is projected to achieve significant growth by the end of the forecast period as per the research study conducted by FutureWise research analysts. (futurewiseresearch.com)

Some factors that affect the width of a confidence interval include: size of the sample, confidence level, and variability within the sample. (calculator.net)
As the sample sizes increase, the variability of each sampling distribution decreases so that they become increasingly more leptokurtic. (thelittleaussiebakery.com)

Sample sizes and margins of error vary from subgroup to subgroup, from year to year and from state to state. (pewresearch.org)
And visit this table to see approximate margins of error for a group of a given size. (pewresearch.org)

Taking the commonly used 95% confidence level as an example, if the same population were sampled multiple times, and interval estimates made on each occasion, in approximately 95% of the cases, the true population parameter would be contained within the interval. (calculator.net)
The size of a sample influences two statistical properties: 1) the precision of our estimates and 2) the power of the study to draw conclusions. (thelittleaussiebakery.com)
You can see the sample size for the estimates in this chart on rollover or in the last column of the table. (pewresearch.org)
Sample size estimates for clinical trials of vasospasm in subarachnoid hemorrhage. (medscape.com)
Estimates are based on household interviews of a sample of the civilian, noninstitutionalized U.S. population and are derived from the National Health Interview Survey sample child component. (cdc.gov)

These factors are the importance of decision, the resource Constraints, the number of variables, the sample sizes used in similar studies, the nature of the research, and the nature of the analysis. (statisticssolutions.com)
Again, if the data collected is on a large number of variables, then the samples should also be large. (statisticssolutions.com)

As defined below, confidence level, confidence intervals, and sample sizes are all calculated with respect to this sampling distribution. (calculator.net)
To learn more about the factors that affect the size of confidence intervals, click here . (surveysystem.com)
Recent studies have shown that the X̄ chart with variable sampling intervals (VSI) and/or with variable sample sizes (VSS) detects process shifts faster than the traditional X̄ chart. (unesp.br)
A Markov chain model is used to determine the properties of the joint X and R charts with variable sample sizes and sampling intervals (VSSI). (unesp.br)
We have a wealth of information on these products' past performance and I'd like to use it to stratify our sample and shrink our confidence intervals a bit. (talkstats.com)

For example, if you asked a sample of 1000 people in a city which brand of cola they preferred, and 60% said Brand A, you can be very certain that between 40 and 80% of all the people in the city actually do prefer that brand, but you cannot be so sure that between 59 and 61% of the people in the city prefer the brand. (surveysystem.com)

The report provides an in-depth anatomy of Blood Analysis Sampling Tube Market trends affecting its growth. (futurewiseresearch.com)

This was a hospital-based, analytical cross-sectional study carried out on 226 symptomatic women wherein cervico-vaginal samples were obtained during gynaecological examination for Pap smears, HPV-DNA and genotype detection with linear array HPV strip, conducted from November 2019 to January 2021. (bvsalud.org)

In statistics, information is often inferred about a population by studying a finite number of individuals from that population, i.e. the population is sampled, and it is assumed that characteristics of the sample are representative of the overall population. (calculator.net)
An FPS system is introduced to fulfill the required characteristics for a sampling device to be used with low and high particle concentrations. (sae.org)
Sample Size and Characteristics. (bvsalud.org)

And when you don't know anything about the population distribution, the thing that we've been doing from the get-go is estimating that character with our sample standard deviation. (khanacademy.org)
So we've been estimating the true standard deviation of the population with our sample standard deviation. (khanacademy.org)
Leave blank if unlimited population size. (calculator.net)
The confidence level is a measure of certainty regarding how accurately a sample reflects the population being studied within a chosen confidence interval. (calculator.net)
A sample is a subset of the population. (statisticssolutions.com)
It is through samples that researchers are able to draw specific conclusions regarding the population. (statisticssolutions.com)
i.e. there is no significant difference in the mean of the sample drawn from the population. (statisticssolutions.com)
For example, if you use a confidence interval of 4 and 47% percent of your sample picks an answer you can be "sure" that if you had asked the question of the entire relevant population between 43% (47-4) and 51% (47+4) would have picked that answer. (surveysystem.com)
The larger your sample size, the more sure you can be that their answers truly reflect the population. (surveysystem.com)
Often you may not know the exact population size. (surveysystem.com)
The mathematics of probability prove that the size of the population is irrelevant unless the size of the sample exceeds a few percent of the total population you are examining. (surveysystem.com)
For this reason, The Survey System ignores the population size when it is "large" or unknown. (surveysystem.com)
Population size is only likely to be a factor when you work with a relatively small and known group of people ( e.g. , the members of an association). (surveysystem.com)
In other words, given a sample size of 100 infections (representing 75% of the total population), a linkage criteria with a specificity of 99% for identifying infections linked by transmission and a specificity of 95%, fewer than 25% of identified pairs will represent true transmission events. (fhcrc.org)
In survey research, 100 samples should be identified for each major sub-group in the population and between 20 to 50 samples for each minor sub-group. (thelittleaussiebakery.com)
The range of the sampling distribution is smaller than the range of the original population. (thelittleaussiebakery.com)
This phenomenon is particularly evident in Gulf countries, such as the United Arab Emirates (UAE) (5), where oil wealth relative to the small population size has prompted rapid socioenvironmental and nutritional shifts. (who.int)
In this case, the errors are the deviations of the observations from the population mean, while the residuals are the deviations of the observations from the sample mean. (wikipedia.org)
The sample mean could serve as a good estimator of the population mean. (wikipedia.org)
To characterize the patterns of attempting to quit smoking and smoking cessation among U.S. adults during 1990 and 1991, CDC's National Health Interview Survey-Health Promotion and Disease Prevention (NHIS-HPDP) supplement collected self-reported information on cigarette smoking from a representative sample of the U.S. civilian, noninstitutionalized population aged greater than or equal to 18 years. (cdc.gov)

Urine and blood samples were collected to test for HIV and select STIs. (who.int)

The standard deviation is inversely proportional to the square root of the sample size. (statisticssolutions.com)

This calculator computes the minimum number of necessary samples to meet the desired statistical constraints. (calculator.net)
Reductions were made to the private industry wage sample sizes, with some constraints. (bls.gov)

This procedure collects a sample of the amniotic fluid that surrounds the unborn baby during pregnancy. (medlineplus.gov)

Minimum stata sample size in stratification? (talkstats.com)

As the leader in sample size technology, PASS performs power analysis and calculates sample sizes for over 1100 statistical test and confidence interval scenarios. (ncss.com)
Enter your choices in a calculator below to find the sample size you need or the confidence interval you have. (surveysystem.com)
This indicates that for a given confidence level, the larger your sample size, the smaller your confidence interval. (surveysystem.com)
However, the relationship is not linear ( i.e. , doubling the sample size does not halve the confidence interval). (surveysystem.com)
To determine the confidence interval for a specific answer your sample has given, you can use the percentage picking that answer and get a smaller interval. (surveysystem.com)

I have noted that in some organisations there are no separate sample that has been tested as a part of the walkthrough and the sample of the walkthrough and the test of operating effectiveness is merged. (sarbanes-oxley-forum.com)
We also include the walkthrough testing in our sample of operating effectiveness testing and they have raised no concern about that either. (sarbanes-oxley-forum.com)
However, some decision makers have a preference for wholly stochastic cost-effectiveness analyses, particularly if the sampled data are derived from randomised controlled trials (RCTs). (nih.gov)
To illustrate how different requirements for wholly stochastic cost-effectiveness evidence could have a significant impact on two of the major determinants of new drug development costs and times, namely RCT sample size and study duration. (nih.gov)
Using data collected prospectively in a clinical evaluation, sample sizes were calculated for a number of hypothetical cost-effectiveness study design scenarios. (nih.gov)
The sample sizes required for the cost-effectiveness study scenarios were mostly larger than those for the baseline clinical trial design. (nih.gov)
Formal requirements for wholly stochastic cost-effectiveness evidence based on the standard frequentist paradigm have the potential to increase the size, duration and number of RCTs significantly and hence the costs and timelines associated with new product development. (nih.gov)
This paper deals with the optimal sample sizes for a multicentre trial in which the cost-effectiveness of two treatments in terms of net monetary benefit is studied. (maastrichtuniversity.nl)
Finally, an expression is derived for calculating optimal and maximin sample sizes that yield sufficient power to test the cost-effectiveness of two treatments. (maastrichtuniversity.nl)

IMSEAR at SEARO: Estimating the Effect of Recurrent Infectious Diseases on Nutritional Status: Sampling Frequency, Sample-size, and Bias. (who.int)
With a suspected and officially conceded frequency of serious "fume/odour" incidents of 1:2000 this sample size is much too small. (anstageslicht.de)

Particle size (10-60 microns). (tkbtrading.com)
Median PM2.5 (particle size ≤ 2.5 µm) mass concentrations were 19.8 µg/m3 (trains), 16.5 µg/m3 (trucks), and 13.9 µg/m3 (background). (cdc.gov)

It displays the sample size and unweighted linkage rates for linkages of NCHS surveys to Medicare Enrollment data. (cdc.gov)
The establishment-sample has 2 parts: a "wage sample" for locality-wage publications, and an "Index subsample" for the Employment Cost Index (ECI) and other publications that use benefits data. (bls.gov)
Larger sample sizes provide more accurate mean values, identify outliers that could skew the data in a smaller sample and provide a smaller margin of error. (thelittleaussiebakery.com)
In general, we found forests to excel at tabular and structured data (vision and audition) with small sample sizes, whereas deep nets performed better on structured data with larger sample sizes. (arxiv.org)
This data has a field containing the size of the tree canopy in feet. (arcgis.com)
We'll use the data in this field to create symbols that represent the real-world size of the tree canopies in relation to other map features, regardless of scale. (arcgis.com)
just 10 students per school, producing such heterogeneous data samples. (coursehero.com)
Sampling, data collection, weighting and tabulation were managed by SSRS in close collaboration with Kaiser Family Foundation and Episcopal Health Foundation researchers. (kff.org)

Where p is the Resistivity is the thickness of the sample, and C.F.1 is the sheet resistance correction factor, which depends on the wafer diameter (d) and the probe tip spacing (s). (mdc-europe.com)

The poll was carried out on a representative sample of physicians in the Nador region. (bvsalud.org)

Smaller sample size produces greater instability with the three-parameter model. (bvsalud.org)

The method assumes an analysis by random effects ordered regression with proportional odds, a reasonable number of clusters, and clusters of the same size. (bl.uk)
Health, malaria was the first reason for consultations in all health facilities (peripheral level, medical centers and A total of 55 vil ages (clusters) were selected as pe proportional to hospitals), accounting for 67.2% of all consultations cluster size technic. (who.int)

Discuss the Effect size and sample size description in orthodontic randomized clinical trials: Are they clear enough? (assignmentlama.com)
Recommended] Discuss the Effect size and sample size description in orthodontic randomized clinical trials: Are they clear enough? (assignmentlama.com)

The patented sample retention system of the NanoDrop 2000 and 2000c spectrophotometers allows a sample to be pipetted directly onto an optical measurement surface. (fishersci.com)

In case of limited information on relevant model parameters, sample size formulas are derived for so-called maximin sample sizes which guarantee a power level at the lowest study costs. (maastrichtuniversity.nl)
Four different maximin sample sizes are derived based on the signs of the lower bounds of two model parameters, with one case being worst compared to others. (maastrichtuniversity.nl)
The aim of the study was to investigate the effect of sample size in the fluctuations of item and person parameters. (bvsalud.org)
Results indicated that item and person parameters can be adequately estimated from samples starting form 200 subjects. (bvsalud.org)
Tooth Size Discrepancies and Arch Parameters among Different Malocclusions in a Jordanian Sample. (bvsalud.org)

The obtained results highlight intrinsic limitations of the liquid jet sampling mode when using 532 nm nanosecond laser pulses with suspensions. (archives-ouvertes.fr)
We show that the occupancy distribution of the collection bins closely correlates with the range of cluster sizes intrinsic to the specific cell line. (nature.com)

Statistical Power The sample size or the number of participants in your study has an enormous influence on whether or not your results are significant. (thelittleaussiebakery.com)
Sample size refers to the number of participants or observations included in a study. (thelittleaussiebakery.com)
Which study requires largest sample size? (thelittleaussiebakery.com)
Which of the following study types would require the largest sample size? (thelittleaussiebakery.com)
What is a good sample size for a quantitative study? (thelittleaussiebakery.com)
The findings of the study provide guidance for choosing an appropriate sampling strategy to explore this association. (who.int)
The study is limited by its retrospective design and small sample size. (aaos.org)
A multicentre cross-sectional study was conducted from 21 July to 17 December 2020 in 3 teaching hospitals in Egypt among a convenience sample of asthma patients. (who.int)

Having a tough time trying to decide which colors to sample try them all! (honeybeegardens.com)
Our samples pack contains samples of all in stock lipstick colors. (honeybeegardens.com)
Please note, samples are only available in select sizes and colors based on availability. (crossvilleinc.com)
Simply edit the sample text below or change colors and size. (fonts.com)

It has some mean, so this is your mean of your sampling distribution still. (khanacademy.org)
Note that using z-scores assumes that the sampling distribution is normally distributed, as described above in "Statistics of a Random Sample. (calculator.net)

As a general rule, sample sizes of 200 to 300 respondents provide an acceptable margin of error and fall before the point of diminishing returns. (thelittleaussiebakery.com)

Given the small size of the adjustments made, we really can't say that. (footballoutsiders.com)

Results for students in the TUDA samples are also included in state and national samples with appropriate weighting. (nationsreportcard.gov)
An asterisk (*) marks results based on small sample sizes. (truedelta.com)
For results based on subgroups, the margin of sampling error may be higher. (kff.org)
The results ranged from 0.033 mg/kg in a sample from Fisher Branch to 1.6 mg/kg in Lundar. (gov.mb.ca)
From the 226 women whose cervical samples were collected for Pap smears, 71 (31.4%) had abnormal cytology results while 155 (68.6%) had normal results. (bvsalud.org)

This thesis aims to provide a unique contribution towards the review and development of sample size methods for CRTs, with a focus on ordinal outcomes. (bl.uk)
For profiling assays, in which a large variety of cellular features are measured to identify similarities among samples, and hence designed to have multiple readouts, several different positive controls for each desired class of outcomes may be necessary. (nih.gov)
Given the positive outcomes obtained with a small sample size, additional research is awarded. (prlog.org)

A self-designed forced-choice questionnaire was distributed to 100 women using random sampling technique. (bvsalud.org)

A set of R functions for calculating sample size requirements using three different Bayesian criteria in the context of a binomial experiment. (mcgill.ca)

Find the square distance from each of these points to your sample mean, add them up, divide by n minus 1, because it's a sample, then take the square root, and you get your sample standard deviation. (khanacademy.org)
Sample standard deviation is 1.04. (khanacademy.org)
So if we don't know that the best thing we can put in there is our sample standard deviation. (khanacademy.org)
tailoring , styling , construction , materials , and components must match the standard reference sample on file with the agency . (lawinsider.com)
Written specifications attempt to describe key requirements of a 3D garment and cannot do so adequately and therefore silence of the specifications does not absolve bidders from matching with precision the standard reference sample. (lawinsider.com)
In addition, stability of the CVS-based standard sampling systems and the FPS system is discussed. (sae.org)

I'm designing a methodology to track the effects of a price test at work, and I'm curious to know whether there are limits on how many strata I can use in a sample or on how many subjects need to be in each strata. (talkstats.com)

The sampling and screening procedures included an oversample component designed to increase the number of respondents ages 18-64 with Medicaid or non-group health insurance coverage. (kff.org)
For the landline sample, respondents were selected by asking for the youngest adult male or female currently at home based on a random rotation. (kff.org)

Your accuracy also depends on the percentage of your sample that picks a particular answer. (surveysystem.com)
For a karyotype test, the type of sample you provide depends on the reason for the test. (medlineplus.gov)

Margin of Error and Sample size. (brainmass.com)
If 99% of your sample said "Yes" and 1% said "No," the chances of error are remote, irrespective of sample size. (surveysystem.com)
In contrast, recall error can lead to exaggerated effect sizes. (who.int)
The margin of sampling error including the design effect for the full sample is plus or minus 3 percentage points. (kff.org)
Sample sizes and margins of sampling error for subgroups are available by request. (kff.org)
Note that sampling error is only one of many potential sources of error in this or any other public opinion poll. (kff.org)

Whether interrogating hundreds of thousands of individual fixed samples or fewer samples collected over time, automated image analysis has become necessary to identify interesting samples and extract quantitative information by microscopy. (nih.gov)

NOTE: The sample size is rounded to the nearest hundred. (nationsreportcard.gov)
Please note that sample items cannot be returned. (honeybeegardens.com)
1] Note: the above equation and the table are only valid for junctions diffused on one side of the sample. (mdc-europe.com)
Note that, because of the definition of the sample mean, the sum of the residuals within a random sample is necessarily zero, and thus the residuals are necessarily not independent . (wikipedia.org)

Rectangular samples should be tested with the length parallel to the probe tips and the width should be taken as d when determining the correction factor. (mdc-europe.com)

Larger samples would be required for conclusive research, such as descriptive surveys. (statisticssolutions.com)
Descriptive studies and correlational studies often require very large samples. (thelittleaussiebakery.com)

Methods I provide a comprehensive review of sample size methods for CRTs and summarise the methodological gaps that remain. (bl.uk)
Sampling size and sampling methods. (academicjournals.org)

How do you know if a sample size is statistically significant? (thelittleaussiebakery.com)

Does this not in effect causes the sample size to be lower than the recommended number by 1. (sarbanes-oxley-forum.com)
What is the difference between statistical significance and effect size? (thelittleaussiebakery.com)
Effect size is not the same as statistical significance: significance tells how likely it is that a result is due to chance, and effect size tells you how important the result is. (thelittleaussiebakery.com)
What is effect size in research? (thelittleaussiebakery.com)
Effect size is a simple way of quantifying the difference between two groups that has many advantages over the use of tests of statistical significance alone. (thelittleaussiebakery.com)
Effect size emphasises the size of the difference rather than confounding this with sample size. (thelittleaussiebakery.com)
A number of alternative measures of effect size are described. (thelittleaussiebakery.com)

e.g. where there are 30 samples to be covered under a TOD would it be enough to test only 29 since the walkthrough would have obviously touched upon the control being tested. (sarbanes-oxley-forum.com)
This walkthrough sample is not randomly selected, therefore, would not be added to a randomly generated sample size for test of controls. (sarbanes-oxley-forum.com)
In my 19 years experience, we have never intermingled a walkthrough sample with the test of control samples. (sarbanes-oxley-forum.com)
For example, if you test 100 samples of soil for evidence of acid rain, your sample size is 100. (thelittleaussiebakery.com)
For example, if the analyte is mercury, the laboratory test will determine the amount of mercury in the sample. (cdc.gov)

The NanoDrop 2000c integrates the sample retention system with cuvette capability. (fishersci.com)

The evolution of the volume sampled by laser pulses was estimated as a function of the laser energy applying conditional analysis when analyzing a suspension of micrometric-sized particles of borosilicate glass. (archives-ouvertes.fr)
FutureWise Market Research has illustrated a report on the Blood Analysis Sampling Tube Market. (futurewiseresearch.com)
In spite of its importance, selenium analysis is not routinely done on forages due to the high cost ($58/sample). (gov.mb.ca)

Organisms2

Diseases3

Chemicals and Drugs1

Analytical, Diagnostic and Therapeutic Techniques and Equipment69

Phenomena and Processes26

Disciplines and Occupations9

Anthropology, Education, Sociology and Social Phenomena1

Technology, Industry, Agriculture1

Humanities2

Information Science14

Named Groups3

Health Care64

Geographicals1

The significance of non-significance. (1/2102)

A simulation study of confounding in generalized linear models for air pollution epidemiology. (2/2102)

Laboratory assay reproducibility of serum estrogens in umbilical cord blood samples. (3/2102)

A note on power approximations for the transmission/disequilibrium test. (4/2102)

Comparison of linkage-disequilibrium methods for localization of genes influencing quantitative traits in humans. (5/2102)

Measurement of continuous ambulatory peritoneal dialysis prescription adherence using a novel approach. (6/2102)

Statistical power of MRI monitored trials in multiple sclerosis: new data and comparison with previous results. (7/2102)

Power and sample size calculations in case-control studies of gene-environment interactions: comments on different approaches. (8/2102)

No data available that match "sample size"

Sample Size

Research Design

Data Interpretation, Statistical

Models, Statistical

Randomized Controlled Trials as Topic

Computer Simulation

Binomial Distribution

Models, Genetic

Reproducibility of Results

Bias (Epidemiology)

Clinical Trials as Topic

Algorithms

Polymorphism, Single Nucleotide

Sampling Studies

Treatment Outcome

Epidemiologic Research Design

Genetic Predisposition to Disease

Case-Control Studies

Genotype

Pilot Projects

Statistics as Topic

Biostatistics

Biometry

Bayes Theorem

Gene Frequency

Likelihood Functions

Genome-Wide Association Study

Probability

Statistical Distributions

Monte Carlo Method

Alleles

Publication Bias

Clinical Trials, Phase II as Topic

Risk Factors

Linkage Disequilibrium

Sensitivity and Specificity

Endpoint Determination

Genetics, Population

Genetic Variation

Oligonucleotide Array Sequence Analysis

Linear Models

Polymorphism, Genetic

Meta-Analysis as Topic

Time Factors

Effect Modifier, Epidemiologic

False Positive Reactions

Gene Expression Profiling

Cluster Analysis

Confidence Intervals

Genetic Association Studies

Genetic Markers

Analysis of Variance

Selection Bias

Genetic Processes

Software

Mathematical Computing

Outcome Assessment (Health Care)

Clinical Protocols

Odds Ratio

Cohort Studies

Regression Analysis

Statistics, Nonparametric

Haplotypes

Prospective Studies

Genetic Linkage

Questionnaires

Chromosome Mapping

Prevalence

Neoplasms

Feasibility Studies

Double-Blind Method

Magnetic Resonance Imaging

Genome, Human

Pinaceae

United States

Diagnostic Techniques and Procedures

Periodicals as Topic

Publishing

Multicenter Studies as Topic

Longitudinal Studies