We report here an effect of exposure to ETS on the risk of head and neck cancer. Not only did we find an elevated cancer risk among individuals exposed to ETS, but we also observed dose-response associations for the degree of ETS exposure, adjusting for several potential confounders. These associations and the dose-response relationships were still present when the analysis was restricted to non-active-smoking cases and controls.. This study has several possible limitations. One limitation is potential selection bias, which might have resulted in an overestimate or underestimate of the ETS effect (bias away from or toward null). Using controls from the blood bank may result in potential selection bias because blood donors might be more health oriented. To assess the potential selection bias, we have compared selected demographic and potential risk factors between blood donor controls and non-cancer controls from the Surgical Day Hospital during the same study period at Memorial Sloan-Kettering ...
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Background: Despite major advances in the knowledge of soft tissue sarcoma (STS) during the last decades, no significant improvement in survival has been observed. Detailed data on the prognosis of STS are crucial in order to identify patients who might benefit from more aggressive treatment. Such data can be obtained from properly designed databases; however, the validation of data is crucial in order to obtain valid, reliable results. Furthermore, the majority of prognostic studies in STS have been limited by potential selection bias, low power, and biased estimates due to the statistical methods used, e.g., dichotomizing continuous variables, censoring competing events, as well as not adjusting for important confounders. The overall aim of this thesis was to investigate the prognosis of STS patients using data from the Aarhus Sarcoma Registry (ASR), covering western Denmark in the period from 1979 to 2008. Material and methods: In study I, we systematically validated data in the ASR and ...
In statistics, sampling error is the error caused by observing a sample instead of the whole population.[1] The sampling error is the difference between a sample statistic used to estimate a population parameter and the actual but unknown value of the parameter.[2] An estimate of a quantity of interest, such as an average or percentage, will generally be subject to sample-to-sample variation.[1] These variations in the possible sample values of a statistic can theoretically be expressed as sampling errors, although in practice the exact sampling error is typically unknown. Sampling error also refers more broadly to this phenomenon of random sampling variation. Random sampling, and its derived terms such as sampling error, imply specific procedures for gathering and analyzing data that are rigorously applied as a method for arriving at results considered representative of a given population as a whole. Despite a common misunderstanding, "random" does not mean the same thing as "chance" as this ...
View Notes - 09-SelectionBias from EPID 600 at UNC. Principles of Epidemiology for Public Health (EPID600) Sources of error: Selection bias Victor J. Schoenbach, PhD Department of Epidemiology
TY - JOUR. T1 - Participants in a randomized controlled trial had longer overall survival than non-participants. T2 - a prospective cohort study. AU - Ohno, Shinji. AU - Mukai, Hirofumi. AU - Narui, Kazutaka. AU - Hozumi, Yasuo. AU - Miyoshi, Yasuo. AU - Yoshino, Hiroshi. AU - Doihara, Hiroyoshi. AU - Suto, Akihiko. AU - Tamura, Motoshi. AU - Morimoto, Takashi. AU - Zaha, Hisamitsu. AU - Chishima, Takashi. AU - Nishimura, Reiki. AU - Ishikawa, Takashi. AU - Uemura, Yukari. AU - Ohashi, Yasuo. PY - 2019/8/15. Y1 - 2019/8/15. N2 - Purpose: While some studies show improved outcomes in clinical trial participants as compared to non-participants, existence of such a trial effect has not been proved precisely. Methods: This was a prospective cohort study to compare the prognoses for participants in the randomized controlled trial (SELECT BC) and non-participants. SELECT BC compared S-1 and taxane as first-line treatment for metastatic breast cancer. Non-participants were all patients who met the ...
Main results : We identified two eligible studies with 633 participants. Both included studies compared the use of protocol-directed sedation, specifically protocols delivered by nurses, with usual care. We rated the risk of selection bias due to random sequence generation low for one study and unclear for one study. The risk of selection bias related to allocation concealment was low for both studies. We also assessed detection and attrition bias as low for both studies while we considered performance bias high due to the inability to blind participants and clinicians in both studies. Risk due to other sources of bias, such as potential for contamination between groups and reporting bias, was considered unclear. There was no clear evidence of differences in duration of mechanical ventilation (MD -5.74 hours, 95% CI -62.01 to 50.53, low quality evidence), ICU length of stay (MD -0.62 days, 95% CI -2.97 to 1.73) and hospital length of stay (MD -3.78 days, 95% CI -8.54 to 0.97) between people ...
Bruno Chomel, professor in the Department of Population Health and Reproduction, has been invited to serve a four-year term as an expert in zoonotic disease for the World Health Organization as a member of the International Health Regulations (IHR) Roster of Experts. As such, he would be available for potential selection in an emergency or review committee concerning disease outbreaks that pass between humans and animals. In the event of a public health threat of international concern (such as the H1N1 flu pandemic in 2009), the Director-General of WHO seeks input and expertise from an IHR Emergency Committee.. "I am very honored to serve as an expert on zoonoses for the WHO," Chomel said. "Many of the worlds emerging diseases are zoonotic and our role as veterinarians is to control and prevent these diseases from their animal sources to reduce the risk of transmission to humans in a global, one health approach.". ...
Bruno Chomel, professor in the Department of Population Health and Reproduction, has been invited to serve a four-year term as an expert in zoonotic disease for the World Health Organization as a member of the International Health Regulations (IHR) Roster of Experts. As such, he would be available for potential selection in an emergency or review committee concerning disease outbreaks that pass between humans and animals. In the event of a public health threat of international concern (such as the H1N1 flu pandemic in 2009), the Director-General of WHO seeks input and expertise from an IHR Emergency Committee.. "I am very honored to serve as an expert on zoonoses for the WHO," Chomel said. "Many of the worlds emerging diseases are zoonotic and our role as veterinarians is to control and prevent these diseases from their animal sources to reduce the risk of transmission to humans in a global, one health approach.". ...
Card and Kruegers meta-analysis of the employment effects of minimum wages challenged existing theory. Unfortunately, their meta-analysis confused publication
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Aims: Selective participation may hamper the validity of population-based cohort studies. The resulting bias can be alleviated by linking auxiliary register data to both the participants and the non-participants of the study, estimating propensity scores for participation and correcting for participation based on these. However, registry holders may not be allowed to disclose sensitive data on (invited) non-participants. Our aim is to provide guidance on how adequate bias correction can be achieved by using auxiliary register data but without disclosing information that could be linked to the subset of non-participants. Methods: We show how existing methods can be used to estimate generalisation weights under various data disclosure scenarios where invited non-participants are indistinguishable from uninvited ones. We also demonstrate how the methods can be implemented using Nordic register data. Results: Inverse-probability-of-sampling weights estimated within a random sample of the target ...
Response 3: Noridian recognizes that availability of tissue is very important. However, this is a limited coverage policy with specific data development expectations for coverage (CDD) focusing on a specific sub-group of patients who have already been tested and found to be negative by other technologies AND have tissue available for testing. As stated above, this policy is NOT about NGS testing more generally. The premise of the Drilon paper is that never- and light-smokers have a higher likelihood of having less complex driver mutations than their smoking counterparts. This premise is well founded with some patients having mutations that were missed by an LDT done at the institution. However, short-comings of the study were: its small size, predominance of never smokers, potential patient selection bias due to the ability to re-biopsy, and limited follow-up on treatment outcomes. In addition, because there was no direct comparison to an FDA-approved companion diagnostic, we cannot directly ...
From time to time, an unexpected finding arises from a clinical trial. The surprise may relate to an endpoint for which there was no prior hypothesis, a subgroup that appears inconsistent with the overall treatment effect, or an unduly large treatment effect that exceeds prior expectations. It may relate to treatment benefit or harm.. The cycle of progress in medical research needs to be borne in mind. A new dramatic claim (whether benefit or harm) is often on the basis of a small study. Accordingly, it is prone to exaggerate the issue, even if the study has no design flaw. The issue becomes high profile without adequate recognition of all of the selection biases that have occurred, for example, across multiple analyses (endpoints, trials, and subgroups). If one focuses on the most extreme result, it will look more impressive than is justified.. One then needs to collect more substantial evidence on the issue, for example, continued follow-up, a larger trial, or a meta-analysis of related ...
Downloadable! We present a simple way to estimate the effects of changes in a vector of observable variables X on a limited dependent variable Y when Y is a general nonseparable function of X and unobservables. We treat models in which Y is censored from above or below or potentially from both. The basic idea is to first estimate the derivative of the conditional mean of Y given X at x with respect to x on the uncensored sample without correcting for the effect of changes in x induced on the censored population. We then correct the derivative for the effects of the selection bias. We propose nonparametric and semiparametric estimators for the derivative. As extensions, we discuss the cases of discrete regressors, measurement error in dependent variables, and endogenous regressors in a cross section and panel data context.
Early studies reported high success rates; in one study in 1925, 60% of patients became seizure-free, and another 35% of patients had a 50% reduction in seizure frequency. These studies generally examined a cohort of patients recently treated by the physician (a retrospective study) and selected patients who had successfully maintained the dietary restrictions. However, these studies are difficult to compare to modern trials. One reason is that these older trials suffered from selection bias, as they excluded patients who were unable to start or maintain the diet and thereby selected from patients who would generate better results. In an attempt to control for this bias, modern study design prefers a prospective cohort (the patients in the study are chosen before therapy begins) in which the results are presented for all patients regardless of whether they started or completed the treatment (known as intent-to-treat analysis).[19 ...
Some medical studies follow a cohort of many people for many years, gathering data on them and sometimes their relatives, so reducing the selection biases that creep into single-snapshot studies.
Strengths of our study contain the huge geographic distribution of your nurses plus the nesting within a very well-defined cohort, which decreases the likelihood of selection bias. Moreover, the specificity of our conclusions with the pregnancy interval areas important constraints on doable residual confounding. Exclusively, any element thats not differentially relevant to PM for the duration of pregnancy as opposed to before or immediately after pregnancy is rather not likely to confound our benefits. So, by way of example, Though inhabitants density, a choice to choose folate nutritional supplements throughout pregnancy, or a host of other opportunity confounders (Grey et al. 2013; Kalkbrenner et al. 2012) could possibly be associated explanation with PM2.five exposure, they might be anticipated to become Similarly relevant to PM2.five exposure ahead of or just after pregnancy as for the duration of it ...
Selection bias is common in clinic-based HIV surveillance. Clinics located in HIV hotspots are often the first to be chosen and monitored, while clinics in less prevalent areas are added to the surveillance system later on. Consequently, the estimated HIV prevalence based on clinic data is substantially distorted, with markedly higher HIV prevalence in the earlier periods and trends that reveal much more dramatic declines than actually occur. Using simulations, we compare and contrast the performance of the various approaches and models for handling selection bias in clinic-based HIV surveillance. In particular, we compare the application of complete-case analysis and multiple imputation (MI). Several models are considered for each of the approaches. We demonstrate the application of the methods through sentinel surveillance data collected between 2002 and 2008 from India. Simulations suggested that selection bias, if not handled properly, can lead to biased estimates of HIV prevalence trends and
In this large prospective study, employees representing occupations from the municipalities and county councils as well as the Swedish industry were included. A limitation is the restriction to those employees who reported sickness absence to AFA Insurance. The response rate in our study was relatively low (60%). In an analysis of a potential selection bias, we tested the proportion of employees with disability pension (,0 day) for the years 2000/2001 for those included in the study who answered the questionnaire, compared with those who did not. We found significantly higher levels of disability pension for the non-responders compared with the responders. This is in line with previous research30 indicating poorer health of persons not participating in health studies.. The measures on treatments and change of occupation as well as most baseline-measures were self-reported, and might therefore be subject to recall bias. Moreover, we could not establish exactly when the treatments took place. ...
PURPOSE: The aim was to study selective participation and its effect on prevalence estimates in a health survey of affected residents 3 weeks after a man-made disaster in The Netherlands (May 13, 2000). METHODS: All affected adult residents were invited to participate. Survey (questionnaire) data were combined with electronic medical records of residents general practitioners (GPs). Data for demographics, relocation, utilization, and morbidity 1 year predisaster and 1 year postdisaster were used. RESULTS: The survey participation rate was 26% (N = 1171). Women (odds ratio [OR], 1.46; 95% confidence interval [CI], 1.28-1.67), those living with a partner (OR, 2.00; 95% CI, 1.72-2.33), those aged 45 to 64 years (OR, 2.00; 95% CI, 1.59-2.52), and immigrants (OR, 1.50; 95% CI, 1.30-1.74) were more likely to participate. Participation rate was not affected by relocation because of the disaster. Participants in the survey consulted their GPs for health problems in the year before and after the ...
Notably, there is no bias if U has the same relative effect on heart failure risk among obese and normal weight persons. Bias also depends on the prevalence of heart failure and the effects of obesity on heart failure and mortality overall-all of which can be estimated from available data. With these inputs, we first calculate the prevalence of U in obese and normal weight patients with heart failure (p1 and p0, respectively) and then calculate the biased relative risk (RR) for the effect of obesity on mortality in an analysis not adjusting for U as RRm.obese × [1 + (RRm.u − 1) × p1]/[1 + (RRm.u − 1) × p0], where RRm.obese and RRm.u are the true causal effects of obesity and U on mortality in heart failure patients, respectively.14 This formula assumes that the effect of U on mortality is the same in obese and normal weight heart failure patients.. How large would these unmeasured factors have to be to generate the observed data patterns under the "selection bias" causal structure? Using ...
This page discusses the nature and extent of two common problems we see with formal evaluations: selection bias and publication bias.
One of the strangest aspects of our understanding of evolutionary biology is the tendency to conflate a sprawling protean dynamic into a sliver of a phenomenon. Most prominently, evolution is often reduced to a process driven by natural selection, with an emphasis on the natural. When people think of populations evolving they imagine them being buffeted by inclement weather, meteors, or smooth geological shifts. These are all natural, physical phenomena, and they all apply potential selection pressures. But this is not the same as evolution; its just one part. A more subtle aspect of evolution is that much of the selection is due to competition between living organisms, not their relationship to exterior environmental conditions.. The question of what drives evolution is a longstanding one. Stephen Jay Gould famously emphasized of the role of randomness, while Richard Dawkins and others prioritize the shaping power of natural selection. More finely still, there is the distinction between those ...
Our study derives part of its strength from our comprehensive approach apparent from the inclusion of health-related behavioural, psychological and material as well as social determinants. Furthermore, the use of educational status as a proxy for socioeconomic position offered the double advantage of relative stability over a lifespan, and the ease of retrieval and recording. The risk of selection bias was minimized by the choice of educational status, which introduces less reverse causation than its alternative, occupational class and income, as mobility of individuals with poor health into certain strata is less likely to be effected by differences in educational level. Selection bias is more likely to influence health differences by occupational class and income, as occupation and income tends to decrease when an individual become chronically ill [28]. The independent effects of occupation and income were moreover taken into account by making separate adjustments for the effect of each ...
07 How accurate are self-selection selection web surves?0t s? Jelke Betlee Te views expressed in tis paper are tose of te autor(s and do not necessaril reflect te policies of Statistics eterlands Discussion
test in 30 elementary schools with high non-participation rates: ... participation in optional training from 12% to 13.4%, in essential instruction from 3.7% to ...
We achieved a pleasing overall retention rate of 78% at infant age two years. This is comparable to the retention rate of 75% at two years of age recently reported for another Australian RCT of an obesity prevention intervention commencing in infancy. [21] A recent pilot study [22] examining an early feeding intervention with first-time mothers (n=160) reported 69% retention at age 12-months. In these studies the intervention was delivered via six and two home visits respectively and as such had much lower participant burden than NOURISH. The NOURISH retention rate is consistent with other longitudinal nutrition studies such as the dietary intake and anthropometric sub-studies of the well-regarded ALSPAC which had 5-6 year retention rates of 54% [23] and 64% [24]. Consistent with the pattern of selection bias, there was evidence of attrition (retention) bias in both maternal age and education. The potential impact of this bias on outcomes will be considered through planned comprehensive process ...
Randomisation eliminates selection bias: there are, however, other forms of bias we guard against. We also take measures to ensure the external validity of trial results. We will undertake the following:. • Adherence to local guidelines for radiographic assessment will be actively promoted. If not stipulated already, we will encourage the use of the full shoulder trauma series [8]. Documentation including a power point presentation illustrating the full trauma series will be made available as part of the trial materials. A minimum of two radiographic views/projections is required for the assessment of study eligibility.. • At the end of the recruitment period, there will be scrutiny and categorization based on the Neer classification system, using pre-prepared forms, of the baseline radiographs of all randomised patients. This will be performed by an independent panel of musculoskeletal radiologists or orthopaedic surgeons who have experience with the Neer classification [3]. Copies of ...
This course will provide students with an introduction to advanced topics in survey data analysis. In Survey Data Analysis DEMO8014 students are introduced to basic multivariate statistical methods for analysing survey data. The present course will provide several important extensions: (1) dealing with sample selection bias and endogeneity bias in survey data (instrumental variable regression and Heckman selection correction); (2) using panel data to control for unobserved heterogeneity (fixed effects and random effects models); (3) modelling the time to an event (survival analysis) and (4) multi-level modelling for hierarchical or clustered data. Participants will gain experience in using the Stata statistical software package to apply these methods to survey data. ...
Although no other treatments showed any clear or reliable effects, most of the studies included in this review had several problems. Many trials were at an unclear risk of selection bias, and some trials were rated as having high risk of detection bias. We considered it unlikely that blinding of participants or providers would introduce any important bias, and we did not downgrade for this reason. It is possible to blind assessors in studies of psychological interventions, and we considered that any lack of assessor blinding could introduce bias and contribute to downgrading our quality assessment. Only four studies were clearly free of selective outcome reporting, with several studies not reporting all outcomes. All identified trials were at a high risk of bias owing to incomplete outcome data; however, this result reflected a high rate of attrition in studies of this type of population rather than a methodological deficiency in the studies themselves. In addition, the definitions of prodromal, ...
However, when the questions to be answered arise in and from more complex patient populations in which the patient characteristics and interventions are more complex and heterogeneous it become much more difficult to separate out causality from bias,confounding and even random variation.In fact, some times it is more than difficult in that after the trial has been done and analyzed we still do not know the answer we were searching for. Case in point is the recent back surgery for herniated disc versus conservative management RCT published in JAMA. In this instance, there was so much cross over between the two groups as they were randomized that the "intent to treat" analysis was not considered valid and the "as treated analysis" suffers from the very real risk of selection bias which is why we have randomization in the first place. One is left with the disturbing thought that it may not be possible to solve this clinical issue by doing a randomized trial as long as we deal with patients who are ...
Our study had several methodological strengths, including the matching process of villages across the implementation boundaries. While we used propensity score matching using census data from several years before the study, we found that the villages matched well on multiple observed dimensions not used in the matching process, suggesting that the villages were matched on unobserved variables as well. We also focused on health outcomes proximal to the services covered by the scheme, as its circumscribed set of covered services enabled measurement of changes in cause specific mortality even if changes in general population health were difficult to measure.. This study was, however, also limited in several ways. First, it was quasi-experimental in that the scheme was not randomly assigned to villages. This posed several methodological challenges but also presented opportunities for using rigorous approaches designed to reduce selection bias. The northern portion of Karnataka was selected for ...
Jason Thomas research focuses on health and mortality with an emphasis on the social and economic processes that generate inequalities in these outcomes over the life course. His work also explores the intergenerational component of the associations involving health, family structure, and the development of skills and traits in childhood and adolescence. In this work he pursues his interest in quantitative methodology by tackling issues related to sample selection biases, missing data, and unobserved heterogeneity. Dr. Thomas is currently working on a project that seeks to explain the role that experiences early in life play in producing the steepening of the education-mortality gradient in the United States.. ...
We externally validated and compared seven published models for the prediction of CKD onset [14, 15], using a recent 5-year window with well-studied EHR data, typical of UK NHS primary care and chronic disease management. All models discriminated well between patients who developed CKD compared with those who did not. Five models had an associated simplified scoring system, each of which had a similar performance to its parent model. Only two models were well-calibrated to the risk levels in our population [36, 54]. Among the 10 % of patients with highest predicted risks, 48.0 % to 64.5 % actually developed CKD.. Two key strengths of this study are (1) its large sample size and (2) its cohort being based on a geographically-defined population rather than tied to a particular EHR, which minimizes selection bias at enrolment. In addition, whilst five out of seven models had already been externally validated [17, 36, 51, 54, 55, 58] and two had been mutually compared [17], our study is the first ...
This survey was conducted online within the U.S. by Harris Interactive on behalf of CareerBuilder.com among 6,704 U.S. employees (employed full-time; not self-employed) ages 18 and over within the U.S. between November 13 and December 3, 2007. Figures for age, sex, race/ethnicity, education, region and household income were weighted where necessary to bring them into line with their actual proportions in the population. The data have been weighted to reflect the composition of U.S. employees, and propensity score weighting was also used to adjust for respondents propensity to be online. With a pure probability sample of 6,704, one could say with a 95 percent probability that the overall results have a sampling error of +/- 1.3% percentage points. Sampling error for data from sub-samples is higher and varies. However that does not take other sources of error into account. This online survey is not based on a probability sample and therefore no theoretical sampling error can be calculated. A full ...
James Poterba is President of the National Bureau of Economic Research. He is also the Mitsui Professor of Economics at M.I.T ...
Downloadable! In the neighbourhood effects literature, the socialisation mechanism is usually investigated by looking at the association between neighbourhood characteristics and educational attainment. The step in between, that adolescents actually internalise educational norms held by residents, is often assumed. We attempt to fill this gap by looking at how educational commitments are influenced by neighbourhood characteristics. We investigate this process for migrant youth, a group that lags behind in educational attainment compared to native youth, and might therefore be particularly vulnerable to neighbourhood effects. To test our hypothesis we used longitudinal panel data with five waves (N=4179), combined with fixed-effects models which control for a large portion of potential selection bias. These models have an advantage over naïve OLS models in that they predict the effect of change in neighbourhood characteristics on change in educational commitment, and therefore offer a more dynamic
Introduction: Studies of delirium after acute stroke focus on stroke units (SUs). A protective effect of SUs against delirium has been suggested. We hypothesized that selection bias against medically complex patients accounts for this apparent effect.. Methods: An observational cohort of acute ischemic stroke patients was screened for post-stroke delirium. Delirium was diagnosed using the Confusion Assessment Method (CAM). Key patient variables were prospectively recorded including initial NIHSS score and medical complications. Univariate associations with delirium were identified and a logistic regression model was developed for the entire cohort. Separate logistic regression models were also developed for non-stroke unit (NSU) and SU patients. The SU consisted of a specialized stroke ward, step-down stroke unit, and a neuroscience ICU.. Results: Over 10 months 246 patients (56% male, mean 65 years, 29% in NSUs) met inclusion criteria. Delirium occurred in 30 (12%) patients and was less ...
The authors conclude: "[C]ancer care and research are becoming more global and complex as clinicians incorporate new knowledge about the molecular characteristics of the disease, the addition of new and often targeted treatments, [and] greater reliance on shared decision making and patient input while also confronting rising costs. Observational research offers a previously untapped resource to navigate and inform these health care decisions. This research is likely to rapidly expand the evidence base that supports critical aspects of cancer care decision making and that complements the evidence collected in [randomized controlled trials]. The knowledge gained from observational studies will help the cancer care community reach its goal of providing high-quality, evidence-based care to all patients with cancer.". Laura A. Levit, JD, of ASCO, is the corresponding author of the Journal of Clinical Oncology article.. The content in this post has not been reviewed by the American Society of Clinical ...
The number of people with a chronic disease will strongly increase in the next decades. Therefore, prevention of disease becomes increasingly important. The aim of this systematic review was to identify factors that negatively influence participation in population-based disease prevention programs in General Practice and to establish whether the program type is related to non-participation levels. We conducted a systematic review in Pubmed, EMBASE, CINAHL and PsycINFO, covering 2000 through July 6th 2012, to identify publications including information about characteristics of non-participants or reasons for non-participation in population-based disease prevention programs in General Practice. A total of 24 original studies met our criteria, seven of which focused on vaccination, eleven on screening aimed at early detection of disease, and six on screening aimed at identifying high risk of a disease, targeting a variety of diseases and conditions. Lack of personal relevance of the program, younger age,
Primary PTCA has compared favorably with fibrinolytic therapy in the treatment of AMI in a number of randomized controlled trials (8,13,14). These trials largely excluded patients who were fibrinolytic ineligible for various reasons, with the presence of chest pain for ,12 h among them. Although it is widely assumed that these patients benefit from late reperfusion therapy with PTCA, this issue has not been well studied. A study of 139 patients presenting with 6 to 48 h of chest pain with a median time to angioplasty of 15 h found a 5.5% in-hospital mortality rate in patients who had successful primary PTCA (15). Mortality was substantially higher when angioplasty was unsuccessful, or when performed in the presence of cardiogenic shock, advanced age or an ejection fraction ≤30%. However, there was no control group in this trial.. The MATE trial (Medicine vs. Angiography in Thrombolytic Exclusion) randomized fibrinolytic ineligible patients with acute coronary syndromes to early triage ...
List of words make out of Nonparticipants. Anagrams of word Nonparticipants. Words made after scrabbling Nonparticipants. Word Creation helps in Anagrams and Puzzles.
This EULAR task force has defined an RA core set, including both items and instruments to support standardised RA data collection in clinical practice and research. This will enable collaborative research studies and increase comparability across studies.. Unlike most previous core sets, this set was specifically developed keeping clinical feasibility in mind. Importantly, core underscores that the set represents a minimum, acknowledging that individual stakeholders are likely to add items or instruments of particular interest to their own data collection.. Consensus for inclusion was straightforward for the majority of items: 16 of the final 21 items were agreed in the first round of voting. Six additional items were included, and after a ratification survey and discussion, joint surgery was excluded in the subsequent process. Discussion for each item is summarised in table 3 in the online supplementary file 1. Of the 26 items ultimately excluded from the core data set, nine were seen as ...
Of all the potential forms of bias that limit the validity and generalisability of clinical trial findings, selection bias is probably the most important. In the Miceli-Richard study, particularly, a number of aspects regarding the source and characteristics of the participants merit careful consideration.. Firstly, the participants were recruited from general practice. Normally this should be beneficial and reduce the referral selection that accompanies many hospital based studies. However, there were fully 200 recruiting sites giving a very small average recruitment of just 3-4 patients for each practitioner. Apart from the difficulty of standardising the research conduct of 200 study personnel the generalisability of the findings is greatly diminished. It would have been far preferable, and more cost effective, to have enrolled a larger number of participants from a smaller number of centres, thus capturing a greater proportion of representative patients from the total available OA population ...
Selection bias. The manner in which individuals are selected into a study cohort and subsequently into an analysis sample can produce biased results. Diabetics younger than 60 years old have at least double the mortality rate of nondiabetics of the same age [20], meaning that fewer diabetics survive to the age of eligibility for enrollment into studies of AD. Therefore, the diabetic participants in these studies represent a selected subset of individuals, likely with better-controlled, less severe or more recently acquired diabetes and better overall health. Further, death, worsening health and the burden of study participation contribute significantly to the selective depletion of diabetic participants from study cohorts over time. The mortality rate among diabetics aged 60-79 is 30% to 148% higher than among non-diabetics of the same age [20]. This pattern of selective attrition can be seen in longitudinal studies of cognitive decline and AD. For instance, a history of diabetes was predictive ...
Henrikson and colleagues (1) concluded that pain relief by nitroglycerin did not predict disease in 459 patients admitted to the hospital for work-up of possible ischemic heart disease. Many study participants with missing or uninterpretable test results were dropped from the analysis, an important type of selection bias that can be measured (and eliminated) when calculating likelihood ratios (2). In addition, the study involved a highly select subgroup-patients with rest pain occurring during evaluation-rather than all patients presenting with chest pain. However, the most serious threat to the validity and generalizability of Henrikson and colleagues findings ...
In Europe there are more than 20 large longitudinal studies in which the main focus has been or is to study prenatal or early life factors in relation to adult disease risk. Many of them are historical cohort studies, or data collection has started after birth retrospectively at various points of life. The most important historical cohort studies, from the point of view of the fetal origin hypothesis, are the Hertfordshire,4 14Preston,12 21 and Sheffield8 studies, as well as the Helsinki27 and Uppsala28 cohort studies.. The studies to date have had a number of important limitations that complicate interpretation. They have not been able to address the complexities of interactions between environmental and genetic factors in explaining the associations between maternal, fetal, and later life factors in the evolution of adult CVD risk. This is because they have been variously too small; retrospective and therefore subject to survival and selection biases; or prospective, but in children and ...
This paper assesses the methodology employed in longitudinal studies of advertising and youth drinking and smoking behaviors. These studies often are given a causal interpretation in the psychology and public health literatures. Four issues are examined from the perspective of econometrics. First, specification and validation of empirical models. Second, empirical issues associated with measures of advertising receptivity and exposure. Third, potential endogeneity of receptivity and exposure variables. Fourth, sample selection bias in baseline and follow-up surveys. Longitudinal studies reviewed include 20 studies of youth drinking and 26 studies of youth smoking. Substantial shortcomings are found in the studies, which preclude a causal interpretation.
In the literature, use of TEE estimates is inconsistent and a topic of methodological research [25, 26, 39, 49, 51]. The following are examples of methods to distinguish individuals who are under-reporters, plausible reporters and over-reporters or to control for magnitude of over- and under-reporting.. I. The ratio of total energy intake to TEE. Different approaches of using the ratio can be undertaken. A study may exclude individuals based on certain cut-points defined within that study, for example bottom and/or top percentiles and means ±1 standard deviation (Note the standard deviation represents within-individual variation or uncertainty of the ratio). Some more recent studies have suggested statistical adjustment for the ratio to hold degrees of misreporting consistent in a population and stratification of results based on misreporting status to avoid unnecessary loss of power and introduction of unpredictable selection bias [26, 49, 51].. Using the ratio of total energy intake to TEE, ...
Theres also the issue of there being far more demand for reviews than time to do them. Selection of products for review is currently governed by Mikes editorial instincts (selection bias in a positive manner). Products are prioritized by how interesting they are likely to be to our readers, and how likely they are to actually get a positive review (based on a visual inspection and the weight of experience). There is probably a years worth of backlog products in the pipeline, and many products simply never see reviews because they are out of date or irrelevant by the time we get to them. Point being, we already break promises of reviews to manufacturers all the time because we simply dont have time to do every review. Reader-donated money creates obligations towards readers that are likely to be broken unless we can find a way to guarantee that the reviews get done. Guaranteeing that every product that sees a certain level of donation is not the way to do this ...
Infanti JJ, ODea A1, Gibson I, McGuire BE, Newell J, Glynn LG, ONeill C, Connolly SB, Dunne FP. BMC Med Res Methodol. 2014 Jan 24;14:13. doi: 10.1186/1471-2288-14-13.. ...
If a population is finite in size (as all populations are) and if a given pair of parents have only a small number of offspring, then even in the absence of all selective forces, the frequency of a gene will not be exactly reproduced in the next generation because of sampling error. If in a population of 1000 individuals the frequency of a is 0.5 in one generation, then it may by chance be 0.493 or 0.505 in the next generation because of the chance production of a few more or less progeny of each genotype. In the second generation, there is another sampling error based on the new gene frequency, so the frequency of a may go from 0.505 to 0.501 or back to 0.498. This process of random fluctuation continues generation after generation, with no force pushing the frequency back to its initial state because the population has no genetic memory of its state many generations ago. Each generation is an independent event. The final result of this random change in allele frequency is that the ...
If a population is finite in size (as all populations are) and if a given pair of parents have only a small number of offspring, then even in the absence of all selective forces, the frequency of a gene will not be exactly reproduced in the next generation because of sampling error. If in a population of 1000 individuals the frequency of a is 0.5 in one generation, then it may by chance be 0.493 or 0.505 in the next generation because of the chance production of a few more or less progeny of each genotype. In the second generation, there is another sampling error based on the new gene frequency, so the frequency of a may go from 0.505 to 0.501 or back to 0.498. This process of random fluctuation continues generation after generation, with no force pushing the frequency back to its initial state because the population has no genetic memory of its state many generations ago. Each generation is an independent event. The final result of this random change in allele frequency is that the ...
If a population is finite in size (as all populations are) and if a given pair of parents have only a small number of offspring, then even in the absence of all selective forces, the frequency of a gene will not be exactly reproduced in the next generation because of sampling error. If in a population of 1000 individuals the frequency of a is 0.5 in one generation, then it may by chance be 0.493 or 0.505 in the next generation because of the chance production of a few more or less progeny of each genotype. In the second generation, there is another sampling error based on the new gene frequency, so the frequency of a may go from 0.505 to 0.501 or back to 0.498. This process of random fluctuation continues generation after generation, with no force pushing the frequency back to its initial state because the population has no genetic memory of its state many generations ago. Each generation is an independent event. The final result of this random change in allele frequency is that the ...
Rethinking the assessment of risk of bias due to selective reporting: a cross-sectional study. . Biblioteca virtual para leer y descargar libros, documentos, trabajos y tesis universitarias en PDF. Material universiario, documentación y tareas realizadas por universitarios en nuestra biblioteca. Para descargar gratis y para leer online.
Not so bothered about the people and cows... A bit of a self-selection blip given its the only photo taken today - and that was for a different...
Researchers seeking to establish causal relationships frequently control for variables on the purported causal pathway, checking whether the original treatment effect then disappears. Unfortunately, this common approach may lead to biased estimates. In this article, we show that the bias can be avoided by focusing on a quantity of interest called the controlled direct effect. Under certain conditions, the controlled direct effect enables researchers to rule out competing explanations--an important objective for political scientists.
First, researchers clearly define the sample used for each study. This helps readers understand what biases may have been built into the data due to the sample. If possible, researchers will compare the sample to other estimates to help the reader understand further what differences this particular sample may have from the total population. For example, authors often list the age and ethnic backgrounds of the women in the study. They explain where the participants were recruited, and even how many of the eligible women agreed to participate.. Second, researchers repeat previous studies with different samples. Remember, every sample provides an estimate of the true value, and no researcher considers their study to represent the whole picture of a problem. Multiple similar studies help researchers understand where that true value lies, and how differences in the sample change that value. For example, in the discussion or conclusion section of a study researchers will often discuss how the ...
AI bias on black skin diseases. A number of reports have echoed the non inclusiveness of AI tools with a strong bias to caucasian white skin
Sampling biases are the greatest impediment to resolving the history of species richness of fossilizable marine invertebrates in the Phanerozoic. Actual patterns of species richness have remained uncertain because no method is available to compensate for variations in sampling intensity. Data are not obtainable which would permit application of techniques that allow direct compensation for sampling intensity, such as rarefaction, but actual patterns can be estimated with a sampling model designed to account for sampling bias. One can estimate the total species richness of a geologic period if one knows the relative sampling intensity devoted to that period, the original species-abundance distribution of all species that existed during the interval, and the number of species that existed during the Cenozoic. The model presented here is based on the assumption that the species-abundance distributions of fossilizable marine invertebrates were lognormal and that sampling was proportional to sediment ...
Practical and objective instruments to assess pediatric Crohns disease (CD) activity are required for observational research and quality improvement. The objectives were: 1) to determine the feasibility of completing the Pediatric Crohns Disease Activity Index (PCDAI) and the Abbreviated PCDAI (APCDAI); and 2) to create a Short PCDAI by retaining and reweighting the most practical and informative components.
However, we should acknowledge that the present study has several limitations. This study is a retrospective study with inherent limitations including potential selection, measurement and misclassification biases. Because of the long study duration, many radiologists were involved in reading CT findings. There can be inter-observer or intra-observer variation in reading the CT findings between different radiologists. However, as radiologists were unaware of the study aims, measurement errors in reading these CT findings were independent and non-differential. Kloeckner et al. [14] suggested that MRI should be used over CT, as MRI is superior to CT for detection of viable tumor residuals after lipiodol-based TACE. Response rate after the first TACE or recurrence rate during follow-up can be varied according to the evaluation method. In this study, we included only patients who showed complete response by mRECIST criteria at 1-month follow-up CT evaluation after the first TACE. However, there was ...
Six potential cities/counties were investigated for potential selection before Phoenix and Philadelphia were finalized. These two areas were selected due to containing (a) high enough rates of serious crime committed by juveniles; (b) a diverse racial/ethnic mix of potential participants; (c) a sizable enough number of female offenders; (d) a contrast in the way the systems operate; (e) political support for the study and cooperation from the practitioners in the juvenile and criminal justice systems; and (f) the presence of experienced research collaborators to oversee the data collection.. Youth were selected for potential enrollment after a review of court files in each locale revealed that they had been adjudicated (found guilty) of a serious offense. Eligible crimes included all felony offenses with the exception of less serious property crimes, as well as misdemeanor weapons offenses and misdemeanor sexual assault.. Drug offenses constitute a large proportion of all offenses committed by ...
Six potential cities/counties were investigated for potential selection before Phoenix and Philadelphia were finalized. These two areas were selected due to containing (a) high enough rates of serious crime committed by juveniles; (b) a diverse racial/ethnic mix of potential participants; (c) a sizable enough number of female offenders; (d) a contrast in the way the systems operate; (e) political support for the study and cooperation from the practitioners in the juvenile and criminal justice systems; and (f) the presence of experienced research collaborators to oversee the data collection.. Youth were selected for potential enrollment after a review of court files in each locale revealed that they had been adjudicated (found guilty) of a serious offense. Eligible crimes included all felony offenses with the exception of less serious property crimes, as well as misdemeanor weapons offenses and misdemeanor sexual assault.. Drug offenses constitute a large proportion of all offenses committed by ...
0095] Anderson, R. P. (2003). Real vs. artefactual absences in species distributions: Tests for Oryzomys albigularis (Rodentia: Muridae) in Venezuela. Journal of Biogeography 30, 591-605. [0096] Argaez, J. A., J. A. Christen, M. Nakamura, and J. Soberon (2005). Prediction of potential areas of species distributions based on presence-only data. Environmental and Ecological Statistics 12(1), 27-44. [0097] Boyce, M. S., P. R. Vernier, S. E. Nielsen, and F. K. Schmiegelow (2002). Evaluating resource selection functions. Ecological Modelling 15, 281-300. [0098] Busby, J. R. (1991). BIOCLIM--a bioclimate analysis and prediction system. In M. P. Austin and C. R. Margules (Eds.), Nature Conservation: Cost Effective Biological Surveys and Data Analysis, pp. 64-68. Melbourne: CSIRO. [0099] Cadman, M. (2007). Atlas of the Breeding Birds of Ontario, 2001-2005. To appear; draft maps at www.birdsontario.org. [0100] Carpenter, G., A. N. Gillison, and J. Winter (1993). DOMAIN: A _exible modeling procedure for ...
The exact meaning of the medical terminology,Selection Bias - An error in choosing the individuals or groups to take part in a study. Ideally, the subjects in a study should be very similar to one another and to the larger population (for example, all individuals with the same disease or condition) from which they are drawn. If there are important differences, the results of the study may not be valid, is clearly explained in Medindia s glossary of medical terms
The frequency-sampling method is widely used to accommodate nonlinear laser tuning in swept-wavelength interferometric techniques such as optical frequency domain reflectometry (OFDR) and swept-wavelength optical coherence tomography (OCT). In this paper we analyze the frequency-sampling method and identify two sources of sampling errors. One source of error is the limit of an underlying approximation for long interferometer path mismatches and fast laser tuning rates. A second source of error is transmission delays in data acquisition hardware. We show that the measurement system can be configured such that the two error sources cancel to second order. We present experimental verification of sampling error correction using a general swept-wavelength interferometer with a significantly nonlinear laser sweep.. ©2008 Optical Society of America. Full Article , PDF Article ...
The frequency-sampling method is widely used to accommodate nonlinear laser tuning in swept-wavelength interferometric techniques such as optical frequency domain reflectometry (OFDR) and swept-wavelength optical coherence tomography (OCT). In this paper we analyze the frequency-sampling method and identify two sources of sampling errors. One source of error is the limit of an underlying approximation for long interferometer path mismatches and fast laser tuning rates. A second source of error is transmission delays in data acquisition hardware. We show that the measurement system can be configured such that the two error sources cancel to second order. We present experimental verification of sampling error correction using a general swept-wavelength interferometer with a significantly nonlinear laser sweep.. ©2008 Optical Society of America. Full Article , PDF Article ...
Observational research promises to complement experimental research by providing large, diverse populations that would be infeasible for an experiment. Observational research can test its own clinical hypotheses, and observational studies also can contribute to the design of experiments and inform the generalizability of experimental research. Understanding the diversity of populations and the variance in care is one component.
This position is responsible for applications and reports research outcomes usingSAS and other statistical software.. Candidates must have excellent SAS programming skills and the ability toimplement complex data step logic.. Must be comfortable with creating complex analysis data sets derived fromvarious data sources with a careful eye for outliers and errors. Priorexperience with large databases and observational research/epidemiology methodsis strongly desired. Experience in designing user interfaces, standardreporting packages, and analysis tools also highly desired.. Working with Observational Research Manager to conduct epidemiologic researchto support pipeline and marketed products. Close cooperation with internal and external medical experts. Basic Qualifications:. Master s degree in Biostatistics, Public Health, Epidemiology,Pharmacology or other relevant scientific ...
In an ageing population, pain, frailty and disability frequently coexist across a wide range of musculoskeletal diagnoses, but their associations remain incompletely understood. The Investigating Musculoskeletal Health and Wellbeing (IMH&W) study aims to measure and characterise the development and progression of pain, frailty and disability, and to identify discrete subgroups and their associations. The survey will form a longitudinal context for nested research, permitting targeted recruitment of participants for qualitative, observational and interventional studies; helping to understand recruitment bias in clinical studies; and providing a source cohort for cohort randomised controlled trials. IMH&W will comprise a prospective cohort of 10,000 adults recruited through primary and secondary care, and through non-clinical settings. Data collection will be at baseline, and then through annual follow-ups for 4 years. Questionnaires will address demographic characteristics, pain severity (0-10 Numerical
Outline of Randomization Lectures 1. Background and definitions 2. Generation of schedules 3. Implementation (to ensure allocation concealment, sometimes called blinded randomization) 4. Theory behind randomization Readings • Chapter 6 of Friedman, Furberg and DeMets • Supplemental notes for week 3 on the class web site • Other papers are cited in the notes Key Points • A random process should be used to generate treatment allocations or assignments • Treatment allocations should be concealed until the time of randomization - "allocation concealment" is critical to prevent selection bias. Some refer to this as "blinded randomization". (It should not be confused with blinding of treatments). Randomization Assignment of experimental units to treatment by a random process such that neither investigator nor patient knows the treatment to be assigned at the time the patient is registered. Timing of Randomized Trials Considerations • 1st patient (Chalmers) • Strong degree of equipoise ...
A systematic error (an estimate of which is known as a measurement bias) is associated with the fact that a measured value contains an offset. A Weekend With Julia: An R Users Reflections The Famous Julia First off, I am not going to talk much about Julias speed. Science and experiments[edit] When either randomness or uncertainty modeled by probability theory is attributed to such errors, they are "errors" in the sense in which that term is used in statistics; Bias Error Definition There are many sources pf error in collecting clinical data. Systematic errors are errors that are not determined by chance but are introduced by an inaccuracy (as of observation or measurement) inherent in the system.[3] Systematic error may also refer to That being said, one sure way to decrease sampling error but not necessarily decrease sampling bias would be to increase your studys sample size. If testing is done "off line" (perhaps as part of a pilot study) then particular care is needed to ensure that ...
In reports by Bredesen and Messing,15 Holtzman et al,16 Bursztyn et al,17 and Petito et al,18 no stroke patients were found with clinical,15 16 17 imaging,15 16 17 or pathological18 findings of stroke, respectively. Since we cannot be absolutely certain that stroke was not ignored in all these series15 16 17 18 instead of not being reported because it was not seen, bias probably was a factor. Also, in all of these reports15 16 17 18 a good description of patients clinical stages was not provided, and the exact number of AIDS patients is not possible to obtain. Furthermore, in the series of Holtzman et al,16 the authors were only discussing patients with new-onset seizures, and a selection bias had probably occurred. Given these findings, the omission of CVD among the data stated in these reports15 16 17 18 is not absolutely reliable, and it is appropriate to exclude them from further analysis. Most clinical series of HIV-infected patients included predominantly cases in "advanced stage of ...
OBJECTIVES: This study proposes to investigate the association among adherence to guidelines, patients characteristics, and health care expenditures using methods for handling endogeneity and selection bias. ❧ METHODS: The study population consists of the random 5% COPD cohort in Medicare for the time period between 2006 and 2008. Patients are classified in 4 groups based on the percentage of use of appropriate therapy based on the GOLD guidelines among the quarters: Group I) 0% - 25%; Group II) 25% - 50%; Group III) 50% - 75%; and Group IV) 75% - 100%. In the dynamic panel data, the time unit of the panel model is set to three months (quarter). The two part model computes the probability of a patient surviving at a given time period and then computes the expected health care expenditures of that patient, given that he/she has survived. ❧ RESULTS: The unadjusted difference in cost between Group I and Group IV is $1,220 per quarter-patient. After adjusting for all covariates and also for the ...
The Gateshead Millennium Baby Study (GMBS) originated from the observation that slower than expected weight gain in infancy, traditionally known as failure to thrive, but more recently as weight faltering, had never been satisfactorily explained. There were methodological problems associated with much previous research. The first was the use of attained weight criteria to identify slow weight gain in infancy, which confounds poor postnatal weight gain with poor prenatal weight gain. The second was the use of referred samples of children, leading to selection biases. The third was the use of retrospective accounts from parents after poor weight gain had already been identified. The GMBS was thus originally designed to investigate the antecedents of weight faltering in a population-based prospective study that addressed the main methodological problems of previous research.. ...
We examined in a large prospective primary care study whether pain localization is helpful to discriminate between CHD and other diseases in chest pain patients. Pain localizations of all major chest pain etiologies (CHD, CWS, GERD and psychogenic chest pain) were mainly situated on the left anterior chest and did not help to discriminate between CHD and other diseases.. Strengths of our study are a large primary care based consecutive sample which is highly representative, the prospective design and low drop-out rates during the follow up period. Study procedures such as random audits reduced the possibility of selection bias. An interdisciplinary team of PCPs and cardiologists provided a precise diagnosis as reference standard. As we did not cluster pain localization data but plotted the original drawings with the help of a specially designed computer program we could maintain highest data integrity for graphical and statistical analysis.. As we did not interfere with the work-up provided by ...
Unfortunately ER doc85 you suffer from your own "selection bias". though I agree I see a smaller fraction of simple cellulitis that you do, You see probably only really know about 5% of all diagnosed MRSA patients in the hospital (and trust me they all dont come in with MRSA, we give it to them). Most are diagnosed AFTER being hospitalized. You know about the ones that tell you and the ones with hospital records. In short you dont really have a clue about the vast majority of MRSA patients. I am not blaming you on that one. There is no way to know until the cultures are back which you may (or may not) hear about. Think about it, suddenly with the diagnosis of MRSA on the floor (or c. diff) the gowns, gloves, masks magically appear. Whats the difference between that patient in the ER and the floor otherwise, really nothing besides the knowledge. The spread of MRSA and C-diff in hospitals is obviously been very well documented/published (hence the coverings). I know you know that (the EMT does ...
The apparent ability of rats to voluntarily select a dietary according to the needs of the body was utilized in a study to detect possible metabolic derangements subsequent to a dose of 375 rad whole-body X-irradiation. The animals were allowed free choice selections of various foodstuffs offered in separate containers and the relative amounts of food intake as well as body weights were measured daily. The majority of the rats were able to select diets adequate enough to support normal growth. Upon irradiation at the level employed, rats fed a basal pre-mixed diet lost significantly more body weight than similarly treated rats selecting their own diet. In the over-all pattern, the proportion of casein selected progressively increased whereas that of sucrose decreased subsequent to the irradiation. The selections of yeast and corn oil remained essentially the same. On the third day only, after irradiation, the intake of minerals increased to over 5 times the pre-irradiation level . The selection
Earths energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the data-rich Argo era are colocated with locations of earlier ocean observations, to quantify this error. Our results provide a new OHC estimate with an unbiased mean sampling error and with variability on decadal and multidecadal time scales (signal) that can be reliably distinguished from sampling error (noise) with signal-to-noise ratios higher than 3. The inferred integrated EEI is greater than that reported in previous assessments and is consistent with a reconstruction of the radiative imbalance at the top of atmosphere starting in 1985. We found that changes ...
Earths energy imbalance (EEI) drives the ongoing global warming and can best be assessed across the historical record (that is, since 1960) from ocean heat content (OHC) changes. An accurate assessment of OHC is a challenge, mainly because of insufficient and irregular data coverage. We provide updated OHC estimates with the goal of minimizing associated sampling error. We performed a subsample test, in which subsets of data during the data-rich Argo era are colocated with locations of earlier ocean observations, to quantify this error. Our results provide a new OHC estimate with an unbiased mean sampling error and with variability on decadal and multidecadal time scales (signal) that can be reliably distinguished from sampling error (noise) with signal-to-noise ratios higher than 3. The inferred integrated EEI is greater than that reported in previous assessments and is consistent with a reconstruction of the radiative imbalance at the top of atmosphere starting in 1985. We found that changes ...
This Harris Poll was conducted online, in English, within the United States between July 16 and 21, 2014 among 2,306 adults (aged 18 and over). Figures for age, sex, race/ethnicity, education, region and household income were weighted where necessary to bring them into line with their actual proportions in the population. Propensity score weighting was also used to adjust for respondents propensity to be online.. All sample surveys and polls, whether or not they use probability sampling, are subject to multiple sources of error which are most often not possible to quantify or estimate, including sampling error, coverage error, error associated with nonresponse, error associated with question wording and response options, and post-survey weighting and adjustments. Therefore, The Harris Poll avoids the words "margin of error" as they are misleading. All that can be calculated are different possible sampling errors with different probabilities for pure, unweighted, random samples with 100% ...
Purpose: Despite the volume of available literature focusing on marathon running and the prediction of performance, no single prediction equations exists that is accurate for all runners of varying experiences and abilities. Indeed the relative merits and utility of the existing equations remain unclear. Thus, the aim of this study was to collate, characterize, compare, and contrast all available marathon prediction equations. Methods: A systematic review was conducted to identify observational research studies outlining any kind of prediction algorithm for marathon performance. Results: Thirty-six studies with 114 equations were identified. Sixty-one equations were based on training and anthropometric variables, whereas 53 equations included variables that required laboratory tests and equipment. The accuracy of these equations was denoted via a variety of metrics; r2 values were provided for 68 equations (r2 = .10-.99), and an SEE was provided for 19 equations (SEE 0.27-27.4 min). Conclusion: ...
Applications to access CPRD data for observational research are reviewed by the Independent Scientific Advisory Committee (ISAC). Approval by ISAC is required for researchers to carry out their proposed studies.. A summary of all ISAC-approved protocols, including a lay and technical summary of the proposed research, is published three months after researchers have access to the data to begin their study.. The table below includes all ISAC-approved protocols submitted to CPRD from 1st July 2015. Searches can be carried out using applicant names, approval date or by using key words within the protocol title. Protocols below are listed in order of date of approval.. Peer-reviewed publications from research using CPRD data will be listed on our bibliography page. ...
%%excerpt%%Bias can infect AI algorithms, and the source of that bias can come from training data, coders who build algorithms and even the corporate culture.
MH supply Satin Polyester Bias Binding, Poly-Cotton Bias Binding, Bias Piping Cord, T/C Bias Binding, Metallic Bias Binding, PU Leather Bias Binding etc
BACKGROUND: Individual participant data (IPD) meta-analyses that obtain raw data from studies rather than summary data typically adopt a two-stage approach to analysis whereby IPD within trials generate summary measures, which are combined using standard meta-analytical methods. Recently, a range of one-stage approaches which combine all individual participant data in a single meta-analysis have been suggested as providing a more powerful and flexible approach. However, they are more complex to implement and require statistical support. This study uses a dataset to compare two-stage and one-stage models of varying complexity, to ascertain whether results obtained from the approaches differ in a clinically meaningful way. METHODS AND FINDINGS: We included data from 24 randomised controlled trials, evaluating antiplatelet agents, for the prevention of pre-eclampsia in pregnancy. We performed two-stage and one-stage IPD meta-analyses to estimate overall treatment effect and to explore potential
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The objective was to determine the risk of sampling error in amniocentesis and chorionic villus sampling (CVS) in singleton and multiple pregnancies. Data from this and other published studies were used to discuss current practice guidelines for mole
Among the 155 interviews audited for quality control, only 25 of them (16.1%) had to change something in the records. Most the corrections were about identification data; in only six records (3.8%) the supervisor had to update morbidity data.. Discussion. This study presents an example of a simple and viable method of teleresearch in reproductive health to trace a specific subject selected from a database carried out in Brazil. Although telephone surveys have been used to explore information on health in developed settings for several years 1,15, there is still some discussion on the validity of telephone surveys for the administration of questionnaires and the mode of contact can interfere in response rates and account for selection bias in public health research. The validity of this method of collecting data needs a high rate of response to truly represent the studied population, therefore it is important to use recruitment methods that are easily reproducible 8,9,16,17.. In our study the ...
This study looks at household contacts of a notified pertussis case and the impact that vaccination and antibiotic usage has on transmission. It identifies several methodological problems with household studies of pertussis including selection bias if using notified cases, lack of consistency in sensitivity when using case definition/clinical history to determine case status, and the importance of controlling for antibiotic treatment in studies of household transmission estimating vaccine effectiveness.
My other concern is that I cant get from Dr. Kendricks article if the original paper is talking about the number of people who develop ALS and report statin use or if its the number of people using statins who have developed ALS. If its the former, it doesnt show causation necessarily. ALS is primarily diagnosed in people over age 55, which is also the prime age where doctors put people on statins, so of course there are more people reporting using statins who have ALS. If its the latter, yeah, thats a concern, but how complete is the data? Since ALS isnt a reportable disease, there could be selection bias in any voluntary reporting to government agencies.. Theres also the difficulty in determining if there has, in fact, been a rise in ALS since the introduction of statins 20 years ago. Dr. Kendrick admitted he couldnt find a clear pattern, partially due to the fact that its not a reportable disease. The CDC has an ALS Registery since 2010, but its voluntary, so theres selection ...
Economic impacts of unionization on employers are difficult to estimate in the absence of large, representative data on establishments with union status information. Estimates are also confounded by selection bias, because unions could organize at highly profitable enterprises that are more likely to grow and pay higher wages. Using multiple establishment-level data sets that represent establishments that faced organizing drives in the U.S. during 1984-1999, this paper uses a regression discontinuity design to estimate the impact of unionization on business survival, employment, output, productivity, and wages. Essentially, outcomes for employers where unions barely won the election (e.g. by one vote) are compared to those where the unions barely lost. The analysis finds small impacts on all outcomes that we examine; estimates for wages are close to zero. The evidence suggests that at least in recent decades the legal mandate that requires the employer to bargain with a certified union has had ...
Huff sets up his headline: "The average Yaleman, Class of 1924, makes $25,111 a year!" said Time magazine, half a century ago. That figure sounded pretty high: Huff chases it, and points out the flaws. How did they find all these people they asked? Who did they miss? Losers tend to drop off the alma mater radar, whereas successful people are in Whos Who and the College Record. Did this introduce "selection bias" into the sample? And how did they pose the question? Can that really be salary rather than investment income? Can you trust people when they self-declare their income? Is the figure spuriously precise? And so on.. In the intervening fifty years this book has sold one and a half million copies, its the greatest selling stats book of all time (tough market) and it remains in print, at just eight pounds ninety nine.. Meanwhile "Doctors say no to abortions in their surgeries" is the headline in the Daily Telegraph. "Family doctors are threatening a revolt against Government plans to allow ...
Lets just put it this way: The Clashs immortal classic "The Guns of Brixton," this aint.. I didnt know whether to laugh or cry after I listened to this song. I also kept holding out hope that The Refusers were some sort of mischievous, clever parody of anti-vaccine nonsense. They arent. Theyre dead serious. In fact, I was originally going to post these lyrics and ask you, my readers, whether they were real or whether I (or some other mischief-maker) made them up as a parody. Unfortunately, Sullivan beat me to the idea. As Ken Reibel put it, all thats missing are the tricorner hats and muskets. Its the soundtrack for an anti-vaccine Tea Party.. As hard as it is to believe, these lyrics are absolutely real and appear to be intended completely sincerely. The Refusers will be performing in Grant Park a mere week from today, leaving me with only two observations.. One: The anti-vaccine movement has degenerated to the point where it is impossible to distinguish real from parody. Its just like ...
Preface; Part I. Introduction: 1. Judgment under uncertainty: heuristics and biases Amos Tversky and Daniel Kahneman; Part II. Representativeness: 2. Belief in the law of small numbers Amos Tversky and Daniel Kahneman; 3. Subjective probability: a judgment of representativeness Daniel Kahneman and Amos Tversky; 4. On the psychology of presiction Daniel Kahneman and Amos Tversky; 5. Studies of representativeness Maya Bar-Hillel; 6. Judgments of and by representativeness Amos Tversky and Daniel Kahneman; Part III. Causality and Attribution: 7. Popular induction: information is not necessarily informative Richard E. Nisbett, Eugene Borgida, Rick Crandall and Harvey Reed; 8. Causal schemas in judgments under uncertainty Amos Tversky and Daniel Kahneman; 9. Shortcomings in the attribution process: on the origins and maintenance of erroneous social assessments Lee Ross and Craig A. Anderson; 10. Evidential impact of base rates Amos Tversky and Daniel Kahneman; Part IV. Availability: 11. Availability: ...
Unlike many of the short-term indicators we publish, there is no simple way of measuring the accuracy of the Blue Book dataset. All estimates, by definition, are subject to statistical uncertainty and for many well-established statistics we measure and publish the sampling error and non-sampling error associated with the estimate, using this as an indicator of accuracy. Since sampling is typically done to determine the characteristics of a whole population, the difference between the sample and population values is considered a sampling error. Non-sampling errors are a result of deviations from the true value that are not a function of the sample chosen, including various systematic errors and any other errors that are not due to sampling. The Blue Book dataset, however, is currently constructed from various data sources, some of which are not based on random samples or do not have published sampling and non-sampling errors available, making it very difficult to measure both error aspects and ...
Researchers should respect the following rights statement: This dataset is given a licence following http://creativecommons.org/licenses/by-nc/3.0/ Norms for data use and publication is based on http://www.canadensys.net/norms Give credit where credit is due. As is common practice in scientific research, cite the data you are using. Be responsible. Use the data responsibly. The data are published to allow anyone to better study and understand the world around us, so please do not use the data in any way that is unlawful, harmful or misleading. Understand that the data are subject to change, errors and sampling bias. Protect the reputation of the data publisher and clearly indicate any changes you may have made to the data. Share knowledge Let us know if you have used the data. It helps our participants to showcase their efforts and it helps you reach a wider audience. Inform the data publisher(s) if you have comments about the data, notice errors, or want more information. Respect the data ...