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.
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 comparison of the quantity of meaningful data to the irrelevant or incorrect data.
A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.
Computer-based representation of physical systems and phenomena such as chemical processes.
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.
A stochastic process such that the conditional probability distribution for a state at any future instant, given the present state, is unaffected by any additional knowledge of the past history of the system.
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.
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)
The study of chance processes or the relative frequency characterizing a chance process.
Application of statistical procedures to analyze specific observed or assumed facts from a particular study.
Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.

An evaluation of elongation factor 1 alpha as a phylogenetic marker for eukaryotes. (1/5116)

Elongation factor 1 alpha (EF-1 alpha) is a highly conserved ubiquitous protein involved in translation that has been suggested to have desirable properties for phylogenetic inference. To examine the utility of EF-1 alpha as a phylogenetic marker for eukaryotes, we studied three properties of EF-1 alpha trees: congruency with other phyogenetic markers, the impact of species sampling, and the degree of substitutional saturation occurring between taxa. Our analyses indicate that the EF-1 alpha tree is congruent with some other molecular phylogenies in identifying both the deepest branches and some recent relationships in the eukaryotic line of descent. However, the topology of the intermediate portion of the EF-1 alpha tree, occupied by most of the protist lineages, differs for different phylogenetic methods, and bootstrap values for branches are low. Most problematic in this region is the failure of all phylogenetic methods to resolve the monophyly of two higher-order protistan taxa, the Ciliophora and the Alveolata. JACKMONO analyses indicated that the impact of species sampling on bootstrap support for most internal nodes of the eukaryotic EF-1 alpha tree is extreme. Furthermore, a comparison of observed versus inferred numbers of substitutions indicates that multiple overlapping substitutions have occurred, especially on the branch separating the Eukaryota from the Archaebacteria, suggesting that the rooting of the eukaryotic tree on the diplomonad lineage should be treated with caution. Overall, these results suggest that the phylogenies obtained from EF-1 alpha are congruent with other molecular phylogenies in recovering the monophyly of groups such as the Metazoa, Fungi, Magnoliophyta, and Euglenozoa. However, the interrelationships between these and other protist lineages are not well resolved. This lack of resolution may result from the combined effects of poor taxonomic sampling, relatively few informative positions, large numbers of overlapping substitutions that obscure phylogenetic signal, and lineage-specific rate increases in the EF-1 alpha data set. It is also consistent with the nearly simultaneous diversification of major eukaryotic lineages implied by the "big-bang" hypothesis of eukaryote evolution.  (+info)

Unusually high evolutionary rate of the elongation factor 1 alpha genes from the Ciliophora and its impact on the phylogeny of eukaryotes. (2/5116)

The elongation factor 1 alpha (EF-1 alpha) has become widely employed as a phylogenetic marker for studying eukaryotic evolution. However, a disturbing problem, the artifactual polyphyly of ciliates, is always observed. It has been suggested that the addition of new sequences will help to circumvent this problem. Thus, we have determined 15 new ciliate EF-1 alpha sequences, providing for a more comprehensive taxonomic sampling of this phylum. These sequences have been analyzed together with a representation of eukaryotic sequences using distance-, parsimony-, and likelihood-based phylogenetic methods. Such analyses again failed to recover the monophyly of Ciliophora. A study of the substitution rate showed that ciliate EF-1 alpha genes exhibit a high evolutionary rate, produced in part by an increased number of variable positions. This acceleration could be related to alterations of the accessory functions acquired by this protein, likely to those involving interactions with the cytoskeleton, which is very modified in the Ciliophora. The high evolutionary rate of these sequences leads to an artificial basal emergence of some ciliates in the eukaryotic tree by effecting a long-branch attraction artifact that produces an asymmetric topology for the basal region of the tree. The use of a maximum-likelihood phylogenetic method (which is less sensitive to long-branch attraction) and the addition of sequences to break long branches allow retrieval of more symmetric topologies, which suggests that the asymmetric part of the tree is most likely artifactual. Therefore, the sole reliable part of the tree appears to correspond to the apical symmetric region. These kinds of observations suggest that the general eukaryotic evolution might have consisted of a massive radiation followed by an increase in the evolutionary rates of certain groups that emerge artificially as early branches in the asymmetric base of the tree. Ciliates in the case of the EF-1 alpha genes would offer clear evidence for this hypothesis.  (+info)

Interaction of process partitions in phylogenetic analysis: an example from the swallowtail butterfly genus Papilio. (3/5116)

In this study, we explored how the concept of the process partition may be applied to phylogenetic analysis. Sequence data were gathered from 23 species and subspecies of the swallowtail butterfly genus Papilio, as well as from two outgroup species from the genera Eurytides and Pachliopta. Sequence data consisted of 1,010 bp of the nuclear protein-coding gene elongation factor-1 alpha (EF-1 alpha) as well as the entire sequences (a total of 2,211 bp) of the mitochondrial protein-coding genes cytochrome oxidase I and cytochrome oxidase II (COI and COII). In order to examine the interaction between the nuclear and mitochondrial partitions in a combined analysis, we used a method of visualizing branch support as a function of partition weight ratios. We demonstrated how this method may be used to diagnose error at different levels of a tree in a combined maximum-parsimony analysis. Further, we assessed patterns of evolution within and between subsets of the data by implementing a multipartition maximum-likelihood model to estimate evolutionary parameters for various putative process partitions. COI third positions have an estimated average substitution rate more than 15 times that of EF-1 alpha, while COII third positions have an estimated average substitution rate more than 22 times that of EF-1 alpha. Ultimately, we found that although the mitochondrial and nuclear data were not significantly incongruent, homoplasy in the fast-evolving mitochondrial data confounded the resolution of basal relationships in the combined unweighted parsimony analysis despite the fact that there was relatively strong support for the relationships in the nuclear data. We conclude that there may be shortcomings to the methods of "total evidence" and "conditional combination" because they may fail to detect or accommodate the type of confounding bias we found in our data.  (+info)

Diagnosing anaemia in pregnancy in rural clinics: assessing the potential of the Haemoglobin Colour Scale. (4/5116)

Anaemia in pregnancy is a common and severe problem in many developing countries. Because of lack of resources and staff motivation, screening for anaemia is often solely by clinical examination of the conjunctiva or is not carried out at all. A new colour scale for the estimation of haemoglobin concentration has been developed by WHO. The present study compares the results obtained using the new colour scale on 729 women visiting rural antenatal clinics in Malawi with those obtained by HemoCue haemoglobinometer and electronic Coulter Counter and with the assessment of anaemia by clinical examination of the conjunctiva. Sensitivity using the colour scale was consistently better than for conjunctival inspection alone and interobserver agreement and agreement with Coulter Counter measurements was good. The Haemoglobin Colour Scale is simple to use, well accepted, cheap and gives immediate results. It shows considerable potential for use in screening for anaemia in antenatal clinics in settings where resources are limited.  (+info)

Laboratory assay reproducibility of serum estrogens in umbilical cord blood samples. (5/5116)

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)

Maximum-likelihood generalized heritability estimate for blood pressure in Nigerian families. (6/5116)

Elevated blood pressure (BP) is more common in relatives of hypertensives than in relatives of normotensives, indicating familial resemblance of the BP phenotypes. Most published studies have been conducted in westernized societies. To assess the ability to generalize these estimates, we examined familial patterns of BP in a population-based sample of 510 nuclear families, including 1552 individuals (320 fathers, 370 mothers, 475 sons, and 387 daughters) from Ibadan, Nigeria. The prevalence of obesity in this community is low (body mass index: fathers, 21.6; mothers, 23.6; sons, 19.2; and daughters=21.0 kg/m2). The BP phenotype used in all analyses was created from the best regression model by standardizing the age-adjusted systolic blood pressure (SBP) and diastolic blood pressure (DBP) to 0 mean and unit variance. Heritability was estimated by use of the computer program SEGPATH from the most parsimonious model of "no spouse and neither gender nor generation difference" as 45% for SBP and 43% for DBP. The lack of a significant spouse correlation is consistent with little or no influence of the common familial environment. However, the heritability estimate of <50% for both SBP and DBPs reinforces the importance of the nonshared environmental effect.  (+info)

A gene for X-linked idiopathic congenital nystagmus (NYS1) maps to chromosome Xp11.4-p11.3. (7/5116)

Congenital nystagmus (CN) is a common oculomotor disorder (frequency of 1/1,500 live births) characterized by bilateral uncontrollable ocular oscillations, with onset typically at birth or within the first few months of life. This condition is regarded as idiopathic, after exclusion of nervous and ocular diseases. X-linked, autosomal dominant, and autosomal recessive modes of inheritance have been reported, but X-linked inheritance is probably the most common. In this article, we report the mapping of a gene for X-linked dominant CN (NYS1) to the short arm of chromosome X, by showing close linkage of NYS1 to polymorphic markers on chromosome Xp11.4-p11.3 (maximum LOD score of 3.20, over locus DXS993). Because no candidate gene, by virtue of its function, has been found in this region of chromosome Xp, further studies are required, to reduce the genetic interval encompassing the NYS1 gene. It is hoped that the complete gene characterization will address the complex pathophysiology of CN.  (+info)

A note on power approximations for the transmission/disequilibrium test. (8/5116)

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)

"Likelihood functions" is a statistical concept that is used in medical research and other fields to estimate the probability of obtaining a given set of data, given a set of assumptions or parameters. In other words, it is a function that describes how likely it is to observe a particular outcome or result, based on a set of model parameters.

More formally, if we have a statistical model that depends on a set of parameters θ, and we observe some data x, then the likelihood function is defined as:

L(θ | x) = P(x | θ)

This means that the likelihood function describes the probability of observing the data x, given a particular value of the parameter vector θ. By convention, the likelihood function is often expressed as a function of the parameters, rather than the data, so we might instead write:

L(θ) = P(x | θ)

The likelihood function can be used to estimate the values of the model parameters that are most consistent with the observed data. This is typically done by finding the value of θ that maximizes the likelihood function, which is known as the maximum likelihood estimator (MLE). The MLE has many desirable statistical properties, including consistency, efficiency, and asymptotic normality.

In medical research, likelihood functions are often used in the context of Bayesian analysis, where they are combined with prior distributions over the model parameters to obtain posterior distributions that reflect both the observed data and prior knowledge or assumptions about the parameter values. This approach is particularly useful when there is uncertainty or ambiguity about the true value of the parameters, as it allows researchers to incorporate this uncertainty into their analyses in a principled way.

Bayes' theorem, also known as Bayes' rule or Bayes' formula, is a fundamental principle in the field of statistics and probability theory. It describes how to update the probability of a hypothesis based on new evidence or data. The theorem is named after Reverend Thomas Bayes, who first formulated it in the 18th century.

In mathematical terms, Bayes' theorem states that the posterior probability of a hypothesis (H) given some observed evidence (E) is proportional to the product of the prior probability of the hypothesis (P(H)) and the likelihood of observing the evidence given the hypothesis (P(E|H)):

Posterior Probability = P(H|E) = [P(E|H) x P(H)] / P(E)

Where:

* P(H|E): The posterior probability of the hypothesis H after observing evidence E. This is the probability we want to calculate.
* P(E|H): The likelihood of observing evidence E given that the hypothesis H is true.
* P(H): The prior probability of the hypothesis H before observing any evidence.
* P(E): The marginal likelihood or probability of observing evidence E, regardless of whether the hypothesis H is true or not. This value can be calculated as the sum of the products of the likelihood and prior probability for all possible hypotheses: P(E) = Σ[P(E|Hi) x P(Hi)]

Bayes' theorem has many applications in various fields, including medicine, where it can be used to update the probability of a disease diagnosis based on test results or other clinical findings. It is also widely used in machine learning and artificial intelligence algorithms for probabilistic reasoning and decision making under uncertainty.

Signal-to-Noise Ratio (SNR) is not a medical term per se, but it is widely used in various medical fields, particularly in diagnostic imaging and telemedicine. It is a measure from signal processing that compares the level of a desired signal to the level of background noise.

In the context of medical imaging (like MRI, CT scans, or ultrasound), a higher SNR means that the useful information (the signal) is stronger relative to the irrelevant and distracting data (the noise). This results in clearer, more detailed, and more accurate images, which can significantly improve diagnostic precision.

In telemedicine and remote patient monitoring, SNR is crucial for ensuring high-quality audio and video communication between healthcare providers and patients. A good SNR ensures that the transmitted data (voice or image) is received with minimal interference or distortion, enabling effective virtual consultations and diagnoses.

An algorithm is not a medical term, but rather a concept from computer science and mathematics. In the context of medicine, algorithms are often used to describe step-by-step procedures for diagnosing or managing medical conditions. These procedures typically involve a series of rules or decision points that help healthcare professionals make informed decisions about patient care.

For example, an algorithm for diagnosing a particular type of heart disease might involve taking a patient's medical history, performing a physical exam, ordering certain diagnostic tests, and interpreting the results in a specific way. By following this algorithm, healthcare professionals can ensure that they are using a consistent and evidence-based approach to making a diagnosis.

Algorithms can also be used to guide treatment decisions. For instance, an algorithm for managing diabetes might involve setting target blood sugar levels, recommending certain medications or lifestyle changes based on the patient's individual needs, and monitoring the patient's response to treatment over time.

Overall, algorithms are valuable tools in medicine because they help standardize clinical decision-making and ensure that patients receive high-quality care based on the latest scientific evidence.

A computer simulation is a process that involves creating a model of a real-world system or phenomenon on a computer and then using that model to run experiments and make predictions about how the system will behave under different conditions. In the medical field, computer simulations are used for a variety of purposes, including:

1. Training and education: Computer simulations can be used to create realistic virtual environments where medical students and professionals can practice their skills and learn new procedures without risk to actual patients. For example, surgeons may use simulation software to practice complex surgical techniques before performing them on real patients.
2. Research and development: Computer simulations can help medical researchers study the behavior of biological systems at a level of detail that would be difficult or impossible to achieve through experimental methods alone. By creating detailed models of cells, tissues, organs, or even entire organisms, researchers can use simulation software to explore how these systems function and how they respond to different stimuli.
3. Drug discovery and development: Computer simulations are an essential tool in modern drug discovery and development. By modeling the behavior of drugs at a molecular level, researchers can predict how they will interact with their targets in the body and identify potential side effects or toxicities. This information can help guide the design of new drugs and reduce the need for expensive and time-consuming clinical trials.
4. Personalized medicine: Computer simulations can be used to create personalized models of individual patients based on their unique genetic, physiological, and environmental characteristics. These models can then be used to predict how a patient will respond to different treatments and identify the most effective therapy for their specific condition.

Overall, computer simulations are a powerful tool in modern medicine, enabling researchers and clinicians to study complex systems and make predictions about how they will behave under a wide range of conditions. By providing insights into the behavior of biological systems at a level of detail that would be difficult or impossible to achieve through experimental methods alone, computer simulations are helping to advance our understanding of human health and disease.

Statistical models are mathematical representations that describe the relationship between variables in a given dataset. They are used to analyze and interpret data in order to make predictions or test hypotheses about a population. In the context of medicine, statistical models can be used for various purposes such as:

1. Disease risk prediction: By analyzing demographic, clinical, and genetic data using statistical models, researchers can identify factors that contribute to an individual's risk of developing certain diseases. This information can then be used to develop personalized prevention strategies or early detection methods.

2. Clinical trial design and analysis: Statistical models are essential tools for designing and analyzing clinical trials. They help determine sample size, allocate participants to treatment groups, and assess the effectiveness and safety of interventions.

3. Epidemiological studies: Researchers use statistical models to investigate the distribution and determinants of health-related events in populations. This includes studying patterns of disease transmission, evaluating public health interventions, and estimating the burden of diseases.

4. Health services research: Statistical models are employed to analyze healthcare utilization, costs, and outcomes. This helps inform decisions about resource allocation, policy development, and quality improvement initiatives.

5. Biostatistics and bioinformatics: In these fields, statistical models are used to analyze large-scale molecular data (e.g., genomics, proteomics) to understand biological processes and identify potential therapeutic targets.

In summary, statistical models in medicine provide a framework for understanding complex relationships between variables and making informed decisions based on data-driven insights.

I'm sorry for any confusion, but "Markov Chains" is a term from the field of mathematics and probability theory, not medicine. Markov Chains are mathematical systems that undergo transitions from one state to another according to certain probabilistic rules. They are named after Russian mathematician Andrey Markov. These chains are used in various fields, including computer science, physics, economics, and engineering, but not commonly in medical definitions or contexts.

Genetic models are theoretical frameworks used in genetics to describe and explain the inheritance patterns and genetic architecture of traits, diseases, or phenomena. These models are based on mathematical equations and statistical methods that incorporate information about gene frequencies, modes of inheritance, and the effects of environmental factors. They can be used to predict the probability of certain genetic outcomes, to understand the genetic basis of complex traits, and to inform medical management and treatment decisions.

There are several types of genetic models, including:

1. Mendelian models: These models describe the inheritance patterns of simple genetic traits that follow Mendel's laws of segregation and independent assortment. Examples include autosomal dominant, autosomal recessive, and X-linked inheritance.
2. Complex trait models: These models describe the inheritance patterns of complex traits that are influenced by multiple genes and environmental factors. Examples include heart disease, diabetes, and cancer.
3. Population genetics models: These models describe the distribution and frequency of genetic variants within populations over time. They can be used to study evolutionary processes, such as natural selection and genetic drift.
4. Quantitative genetics models: These models describe the relationship between genetic variation and phenotypic variation in continuous traits, such as height or IQ. They can be used to estimate heritability and to identify quantitative trait loci (QTLs) that contribute to trait variation.
5. Statistical genetics models: These models use statistical methods to analyze genetic data and infer the presence of genetic associations or linkage. They can be used to identify genetic risk factors for diseases or traits.

Overall, genetic models are essential tools in genetics research and medical genetics, as they allow researchers to make predictions about genetic outcomes, test hypotheses about the genetic basis of traits and diseases, and develop strategies for prevention, diagnosis, and treatment.

I'm sorry for any confusion, but the "Monte Carlo method" is actually a term from the field of mathematics and computer science, not medicine. It refers to a statistical technique that allows for the modeling of complex systems by running multiple simulations with random inputs. This method is widely used in various fields such as physics, engineering, and finance, but it is not a medical concept or term.

In the context of medicine and healthcare, 'probability' does not have a specific medical definition. However, in general terms, probability is a branch of mathematics that deals with the study of numerical quantities called probabilities, which are assigned to events or sets of events. Probability is a measure of the likelihood that an event will occur. It is usually expressed as a number between 0 and 1, where 0 indicates that the event is impossible and 1 indicates that the event is certain to occur.

In medical research and statistics, probability is often used to quantify the uncertainty associated with statistical estimates or hypotheses. For example, a p-value is a probability that measures the strength of evidence against a hypothesis. A small p-value (typically less than 0.05) suggests that the observed data are unlikely under the assumption of the null hypothesis, and therefore provides evidence in favor of an alternative hypothesis.

Probability theory is also used to model complex systems and processes in medicine, such as disease transmission dynamics or the effectiveness of medical interventions. By quantifying the uncertainty associated with these models, researchers can make more informed decisions about healthcare policies and practices.

Statistical data interpretation involves analyzing and interpreting numerical data in order to identify trends, patterns, and relationships. This process often involves the use of statistical methods and tools to organize, summarize, and draw conclusions from the data. The goal is to extract meaningful insights that can inform decision-making, hypothesis testing, or further research.

In medical contexts, statistical data interpretation is used to analyze and make sense of large sets of clinical data, such as patient outcomes, treatment effectiveness, or disease prevalence. This information can help healthcare professionals and researchers better understand the relationships between various factors that impact health outcomes, develop more effective treatments, and identify areas for further study.

Some common statistical methods used in data interpretation include descriptive statistics (e.g., mean, median, mode), inferential statistics (e.g., hypothesis testing, confidence intervals), and regression analysis (e.g., linear, logistic). These methods can help medical professionals identify patterns and trends in the data, assess the significance of their findings, and make evidence-based recommendations for patient care or public health policy.

Biological models, also known as physiological models or organismal models, are simplified representations of biological systems, processes, or mechanisms that are used to understand and explain the underlying principles and relationships. These models can be theoretical (conceptual or mathematical) or physical (such as anatomical models, cell cultures, or animal models). They are widely used in biomedical research to study various phenomena, including disease pathophysiology, drug action, and therapeutic interventions.

Examples of biological models include:

1. Mathematical models: These use mathematical equations and formulas to describe complex biological systems or processes, such as population dynamics, metabolic pathways, or gene regulation networks. They can help predict the behavior of these systems under different conditions and test hypotheses about their underlying mechanisms.
2. Cell cultures: These are collections of cells grown in a controlled environment, typically in a laboratory dish or flask. They can be used to study cellular processes, such as signal transduction, gene expression, or metabolism, and to test the effects of drugs or other treatments on these processes.
3. Animal models: These are living organisms, usually vertebrates like mice, rats, or non-human primates, that are used to study various aspects of human biology and disease. They can provide valuable insights into the pathophysiology of diseases, the mechanisms of drug action, and the safety and efficacy of new therapies.
4. Anatomical models: These are physical representations of biological structures or systems, such as plastic models of organs or tissues, that can be used for educational purposes or to plan surgical procedures. They can also serve as a basis for developing more sophisticated models, such as computer simulations or 3D-printed replicas.

Overall, biological models play a crucial role in advancing our understanding of biology and medicine, helping to identify new targets for therapeutic intervention, develop novel drugs and treatments, and improve human health.

Log-likelihood function is a logarithmic transformation of the likelihood function, often denoted by a lowercase l or ℓ {\ ... In that case, concavity of the likelihood function plays a key role. More specifically, if the likelihood function is twice ... In such a situation, the likelihood function factors into a product of individual likelihood functions. The empty product has ... that maximizes the likelihood function, creating an isometric profile of the likelihood function for a given β 1 {\displaystyle ...
Monotone likelihood functions are used to construct uniformly most powerful tests, according to the Karlin-Rubin theorem. ... This task is simplified if the family has the monotone likelihood ratio property (MLRP). A family of density functions { f θ ( ... In statistics, the monotone likelihood ratio property is a property of the ratio of two probability density functions (PDFs). ... H_{1}:\theta >\theta _{0}.} Monotone likelihood-functions are used to construct median-unbiased estimators, using methods ...
In statistics, Whittle likelihood is an approximation to the likelihood function of a stationary Gaussian time series. It is ... In a stationary Gaussian time series model, the likelihood function is (as usual in Gaussian models) a function of the ... Hurvich, C. (2002). "Whittle's approximation to the likelihood function" (PDF). NYU Stern. Calder, M.; Davis, R. A. (1997), "An ... This approximate model immediately leads to the (logarithmic) likelihood function log ⁡ ( P ( x 1 , … , x N ) ) ∝ − ∑ j ( log ...
The term quasi-likelihood function was introduced by Robert Wedderburn in 1974 to describe a function that has similar ... Quasi-maximum likelihood estimate Extremum estimator Wedderburn, R. W. M. (1974). "Quasi-likelihood functions, generalized ... In statistics, quasi-likelihood methods are used to estimate parameters in a statistical model when exact likelihood methods, ... properties to the log-likelihood function but is not the log-likelihood corresponding to any actual probability distribution. ...
Maximum likelihood estimation. Simultaneous equation systems, large econometric models. ARIMA (autoregressive, integrated ... moving average) and transfer function models. Spectral analysis. Kalman filter and State Space models. Neural networks. ...
A likelihood function arises from a probability density function considered as a function of its distributional ... a probability mass function. Two likelihood functions are equivalent if one is a scalar multiple of the other. The likelihood ... In frequentist inference, the likelihood ratio is used in the likelihood-ratio test, but other non-likelihood tests are used as ... but does on the likelihood (in the sense of the likelihood function) of the parameter value being 1/2 . Summary of the ...
The elements of Thompson sampling are as follows: a likelihood function P ( r , θ , a , x ) {\displaystyle P(r,\theta ,a,x)} ; ... is the likelihood function. Thompson sampling consists in playing the action a ∗ ∈ A {\displaystyle a^{\ast }\in {\mathcal {A ... Thompson, William R. "On the likelihood that one unknown probability exceeds another in view of the evidence of two samples". ... likelihoods of the actions a 1 , a 2 , … , a T {\displaystyle a_{1},a_{2},\ldots ,a_{T}} , and then by sampling the action a T ...
... is the likelihood function. C {\displaystyle C} is a constant that cancels out in all calculations that compare different ... AIC requires calculating the likelihood at its maximum over θ {\displaystyle \theta } , which is not readily available from the ... Note that the p in this expression is the predictive distribution rather than the likelihood above. Akaike information ...
This estimating function is often the derivative of another statistical function. For example, a maximum-likelihood estimate is ... a maximum likelihood estimator of θ is computed for each set of data by maximizing the likelihood function over the parameter ... While this ρ function is not differentiable in θ, the ψ-type M-estimator, which is the subgradient of ρ function, can be ... Another popular M-estimator is maximum-likelihood estimation. For a family of probability density functions f parameterized by ...
The ELM predicts that there are a variety of psychological processes of change that operate to varying degrees as a function of ... The elaboration likelihood model (ELM) of persuasion is a dual process theory describing the change of attitudes. The ELM was ... The elaboration likelihood continuum ought to show that a human can undergo a natural progression from high involvement to low ... Elaboration likelihood model is a general theory of attitude change. According to the theory's developers Richard E. Petty and ...
... predicting gene function was done primarily by comparing the gene sequence with the sequences of genes with known functions. ... Bayesian inference or maximum likelihood estimation). When Jonathan Eisen originally coined phylogenomics, it applied to ... However, Eisen noted that H. pylori lacks other genes thought to be essential for this function (specifically, members of the ... Furthermore, he suggested that this "phylogenomic" approach could be used as a general method for prediction functions of genes ...
The innovation estimator for the parameters of the SDE (1) is the one that maximizes the likelihood function of the discrete- ... Ozaki, T.; Jimenez, J. C.; Haggan-Ozaki, V. (2000). "The Role of the Likelihood Function in the Estimation of Chaos Models". ... Schweppe, F. (1965). "Evaluation of likelihood functions for Gaussian signals". IEEE Transactions on Information Theory. 11 (1 ... For smooth enough function h {\displaystyle \mathbf {h} } , nonlinear observation equations of the form z t k = h ( t k , x ( t ...
... likelihood functions do not need to be integrated, and a likelihood function that is uniformly 1 corresponds to the absence of ... These functions, interpreted as uniform distributions, can also be interpreted as the likelihood function in the absence of ... See Likelihood function § Non-integrability for details. Examples of improper priors include: The uniform distribution on an ... Historically, the choice of priors was often constrained to a conjugate family of a given likelihood function, for that it ...
Greene, William H. (1980). "Maximum likelihood estimation of econometric frontier functions". Journal of Econometrics. 13 (1): ...
Owen, A.B. (1995). Nonparametric likelihood confidence bands for a distribution function. Journal of the American Statistical ... A distribution function on the real numbers R {\displaystyle \mathbb {R} } , is a function D : R → [ 0 , 1 ] , {\displaystyle D ... P-boxes are specified by left and right bounds on the distribution function (or, equivalently, the survival function) of a ... A p-box is a set of distributions functions F satisfying the following constraints, for specified distribution functions F F, ...
... the likelihood function of the outputs is analytically intractable; it is given in terms of a multidimensional marginalization ... The functions f {\displaystyle f} and g {\displaystyle g} are general nonlinear functions. The first equation is known as the ... Consequently, commonly used parameter estimation methods such as the Maximum Likelihood Method or the Prediction Error Method ... Neural networks have excellent approximation properties but these are usually based on standard function approximation results ...
These data are incorporated in a likelihood function. The product of the prior and the likelihood, when normalized, results in ... The first law was published in 1774, and stated that the frequency of an error could be expressed as an exponential function of ... The objective wave function evolves deterministically but, according to the Copenhagen interpretation, it deals with ... and stated that the frequency of the error is an exponential function of the square of the error. The second law of error is ...
... neo-Fisherian statistics emphasizes likelihood functions of parameters. Second, Kempthorne was skeptical of Bayesian statistics ... which use not only likelihoods but also probability distributions on parameters. Nonetheless, while subjective probability and ...
The likelihood function for N iid observations (k1, ..., kN) is L ( r , p ) = ∏ i = 1 N f ( k i ; r , p ) {\displaystyle L(r,p ... prod _{i=1}^{N}f(k_{i};r,p)\,\!} from which we calculate the log-likelihood function ℓ ( r , p ) = ∑ i = 1 N ln ⁡ ( Γ ( k i + r ... mass function and obtain the following mass function of the distribution of houses (for n ≥ 5): f ( n ) = ( ( n − 5 ) + 5 − 1 n ... The cumulative distribution function can be expressed in terms of the regularized incomplete beta function: F ( k ; r , p ) ≡ ...
"Nonparametric likelihood confidence bands for a distribution function". Journal of the American Statistical Association. ... spectral density functions, quantile functions, scatterplot smooths, survival functions, and characteristic functions.[citation ... A confidence band is used in statistical analysis to represent the uncertainty in an estimate of a curve or function based on ... In the definition of a pointwise confidence band, that universal quantifier moves outside the probability function. Confidence ...
A marginal likelihood is a likelihood function that has been integrated over the parameter space. In Bayesian statistics, it ... it is often desirable to consider the likelihood function only in terms of ψ {\displaystyle \psi } , by marginalizing out λ {\ ... is the likelihood. The marginal likelihood quantifies the agreement between data and prior in a geometric sense made precise[ ... Writing θ {\displaystyle \theta } for the model parameters, the marginal likelihood for the model M is p ( X ∣ M ) = ∫ p ( X ∣ ...
The effect of introducing the weighting function w(rN) is equivalent to adding a biasing potential V(rN) to the potential ... WHAM can be derived using the Maximum likelihood method. Subtleties exist in deciding the most computationally efficient way to ... A further alternative which functions in full non-equilibrium is S-PRES. Torrie, G. M.; Valleau, J. P. (1977). "Nonphysical ... a function chosen to promote configurations that would otherwise be inaccessible to a Boltzmann-weighted Monte Carlo run. In ...
ABC methods bypass the evaluation of the likelihood function. In this way, ABC methods widen the realm of models for which ... All ABC-based methods approximate the likelihood function by simulations, the outcomes of which are compared with the observed ... For simple models, an analytical formula for the likelihood function can typically be derived. However, for more complex models ... In all model-based statistical inference, the likelihood function is of central importance, since it expresses the probability ...
The second concept is to use ontology-labeled protein domains for, for example, protein function prediction. Put it in a simple ... reconstruction of ancestral discrete characters using maximum likelihood/parsimony. SCOP Pfam InterPro Structural domain Gene ... In the early 2014, the 'dcGO Predictor' was submitted for both function and phenotype predictions, ranked top in 4th in CAFA ... 2013). "A large-scale evaluation of computational protein function prediction". Nature Methods. 10 (3): 221-227. doi:10.1038/ ...
This is done through the calculation shown below, where P ( D , H ) {\displaystyle P(D,H)} is the likelihood function. This ... which states that models or inferences for datasets leading to the same likelihood function should generate the same ... Wald, Abraham (1993). "Statistical Decision Functions". In Kotz, Samuel; Johnson, Norman L. (eds.). Breakthroughs in Statistics ... is misread by judging A's likelihood by how well the evidence X matches A, but crucially without considering the prior ...
In astrophysics, lambda represents the likelihood that a small body will encounter a planet or a dwarf planet leading to a ... In mathematical logic and computer science, lambda is used to introduce anonymous functions expressed with the concepts of ... In statistics, lambda is used for the likelihood ratio. In statistics, Wilks's lambda is used in multivariate analysis of ... Lambda is the von Mangoldt function in mathematical number theory. Lambda denotes the de Bruijn-Newman constant which is ...
This objective function is called the log-likelihood function. Generalized method of moments estimator is defined through the ... Maximum likelihood estimation uses the objective function Q ^ n ( θ ) = log ⁡ [ ∏ i = 1 n f ( x i , θ ) ] = ∑ i = 1 n log ⁡ f ... If the parameter space Θ is compact and there is a limiting function Q0(θ) such that: Q ^ n ( θ ) {\displaystyle \scriptstyle ... The theory of extremum estimators does not specify what the objective function should be. There are various types of objective ...
... functions as a single living organism. The smaller it gets, the less chance the entire bog has of surviving. The ... This increases the likelihood of animal injury and mortality. The construction of Highway 91 has prevented periodic flooding ...
For example, the negative log-likelihood can be directly computed and minimized as the loss function. Additionally, novel ... To efficiently compute the log likelihood, the functions f 1 , . . . , f K {\displaystyle f_{1},...,f_{K}} should be 1. easy to ... is an arbitrary function and can be modeled with e.g. neural networks. The inverse function is then naturally: z 0 = F − 1 ( x ... and generative adversarial network do not explicitly represent the likelihood function. Let z 0 {\displaystyle z_{0}} be a ( ...
The likelihood function for N iid observations (x1, ..., xN) is L ( k , θ ) = ∏ i = 1 N f ( x i ; k , θ ) {\displaystyle L(k,\ ... is the gamma function evaluated at k. The cumulative distribution function is the regularized gamma function: F ( x ; k , θ ... from which we calculate the log-likelihood function ℓ ( k , θ ) = ( k − 1 ) ∑ i = 1 N ln ⁡ ( x i ) − ∑ i = 1 N x i θ − N k ln ... Substituting this into the log-likelihood function gives ℓ ( k ) = ( k − 1 ) ∑ i = 1 N ln ⁡ ( x i ) − N k − N k ln ⁡ ( ∑ x i k ...
Log-likelihood function is a logarithmic transformation of the likelihood function, often denoted by a lowercase l or ℓ {\ ... In that case, concavity of the likelihood function plays a key role. More specifically, if the likelihood function is twice ... In such a situation, the likelihood function factors into a product of individual likelihood functions. The empty product has ... that maximizes the likelihood function, creating an isometric profile of the likelihood function for a given β 1 {\displaystyle ...
... on WN Network delivers the latest Videos and Editable pages for News & Events, including Entertainment, ... Likelihood function. In statistics, a likelihood function (often simply the likelihood) is a function of the parameters of a ... Likelihood functions play a key role in statistical inference, especially methods of estimating a parameter from a set of ... Probability is used when describing a function of the outcome given a fixed parameter value. Likelihood is used when describing ...
Various research teams investigated kidney function decline during the COVID-19 pandemic, including risk factors and biomarkers ... Close more info about COVID-19 Infection Increases Likelihood of Kidney Function Decline ... Close more info about COVID-19 Infection Increases Likelihood of Kidney Function Decline ... Close more info about COVID-19 Infection Increases Likelihood of Kidney Function Decline ...
Why does setting the derivative of a likelihood function equal to 0 maximize the likelihood function? ... How do you Taylor expand the log likelihood function of the Poisson distribution?. Ask Question ... mu_0$ is defined to be the value of $\mu$ which gives the maximum of the likelihood, at which the likelihood has a value $L_0$. ... How to optimize the log likelihood to obtain parameters for the maximum likelihood estimate? ...
Starting from the log-likelihood function for a Gaussian,. $$ \mathcal{L}\mathcal{L} = - \frac{N}{2} \log{\left(2 \pi\sigma^2\ ... How can I prove the maximum likelihood estimate of $\mu$ is actually a maximum likelihood estimate? ... Log-likelihood of Normal Distribution: Why the term $\frac{n}{2}\log(2\pi \sigma^2)$ is not considered in the minimization of ... A similar approach is useful in fitting mixed models, where the profile likelihood with $\mu$ and $\sigma$ profiled out still ...
... that measured perceived family of origin functioning (Beavers & Hampson, 1990), and a demographic questionnaire that included ... indicated that higher levels of unresolved conflict in ones family of origin were significantly related to the likelihood to ... This study was grounded in family systems theory and explored the relationship between family of origin functioning, ... Family of origin functioning and the likelihood of seeking romantic partners over the Internet ...
expected value of a score function (the gradient of the log-likelihood function). Ask Question ... So the distribution function $g(t)$ of $T = \frac{\partial}{\partial y} \log\left[f(x,y)\right]$ is as following:. $$ g(t) = \ ... My question is why the probability density function of random variable $\frac{ \partial }{ \partial \beta } \ln p(X,\beta)$ is ... this is just a function of $X$, hence the pdf is $p(X,\beta)$. ... expected value of a score function should equals to zero and ...
A log-likelihood-gain intensity target for crystallographic phasing that accounts for experimental error ... MLI function. Formulating likelihood functions in terms of intensities avoids a number of the problems described above. A ... is that if the intensity-based likelihood is approximated by a Rice-function likelihood with some amplitude (. ) standing in ... In essence, the LLGI function for accounting for experimental errors in log-likelihood-gain target functions starts by finding ...
The likelihood function for this model is defined by: L. =. ∏. i. =. 1. n. P. (. Y. i. =. y. i. ). =. ∏. i. =. 1. n. (. ∏. j. = ... Likelihood function[edit]. The observed values y. i. ∈. 0. ,. 1. ,. …. K. {\displaystyle y_{i}\in {0,1,\dots K}}. for i. =. 1. ... The following function: softmax. ⁡. (. k. ,. x. 1. ,. …. ,. x. n. ). =. e. x. k. ∑. i. =. 1. n. e. x. i. {\displaystyle \ ... The negative log-likelihood function is therefore the well-known cross-entropy: :. −. log. ⁡. L. =. −. ∑. i. =. 1. n. ∑. j. =. ...
Likelihood Functions* * Logistic Models* * Risk Factors Grants and funding * N01-AI-72631/AI/NIAID NIH HHS/United States ... Maximum likelihood estimation of the attributable fraction from logistic models Biometrics. 1993 Sep;49(3):865-72. ... estimator is not, however, the maximum likelihood estimator (MLE) based on the model, as it uses the model only to construct ... We here provide maximum likelihood estimators for the attributable fraction in cohort and case-control studies, and their ...
The skew normal function to approximate a log likelihood function. Source: R/LikelihoodApproximation.R. skewNormal.Rd. ... The skew normal function. When alpha = 0. this function is the normal distribution. ... Bayesian adaptive bias correction using profile likelihoods * Effect estimate synthesis using non-normal likelihood ...
"The production function," Physica A: Statistical Mechanics and its Applications, Elsevier, vol. 374(2), pages 707-714. * Guido ... "The Production Function," Papers physics/0511191, arXiv.org. * Kumbhakar, Subal C. & Parmeter, Christopher F. & Tsionas, ... "Inference for Nonparametric Productivity Networks: A Pseudo-likelihood Approach," DIAG Technical Reports 2018-06, Department of ...
An Integrated Bayesian/Likelihood Approach presents a unified Bayesian treatment of parameter i ... The likelihood function Theories. Nonmodel-based repeated sampling. Conclusion. The Integrated Bayes/Likelihood Approach. ... I like this book very much … a worthy new tool based on the posterior distribution of the likelihood with good examples of its ... Posterior likelihood approach. Bayes factors The comparison of unrelated models Example-GHQ score and psychiatric diagnosis ...
A marginal likelihood is a likelihood function that has been integrated over the parameter space. In Bayesian statistics, it ... dubious - discuss], it is often desirable to consider the likelihood function only in terms of ψ. {\displaystyle \psi }. , by ... is the likelihood. The marginal likelihood quantifies the agreement between data and prior in a geometric sense made precise[ ... the marginal likelihood in general asks what the probability p. (. X. ∣. α. ). {\displaystyle p(\mathbf {X} \mid \alpha )}. is ...
A closely related concept is that of the likelihood function, which is used to describe goodness of fit for a distribution ... or hazard functions. The distribution functions can be computed for all symbolic distributions whether parametric, ... Distribution functions can be used to show that two distributions are equal in distribution or compare goodness of fit to data ... A similarly closely related concept is that of the generating function, which is a transformed version of the probability ...
This MATLAB function computes the probability of default for the compactCreditScorecard (csc) based on the data. ... function to obtain the probability of default using the newdata. .. newdata = data(10:20,:); pd = probdefault(csc,newdata). ...
Improved Likelihood Function in Particle-based IR Eye Tracking. I Improved Likelihood Function in Particle-based IR Eye ... Improved Likelihood Function in Particle-based IR Eye Tracking. Improved Likelihood Function in Particle-based IR Eye Tracking ... Improved Likelihood Function in Particle-based IR Eye Tracking. I Improved Likelihood Function in Particle-based IR Eye ... Improved Likelihood Function in Particle-based IR Eye Tracking. i Improved Likelihood Function in Particle-based IR Eye ...
Can depression increase the likelihood of rapid kidney function decline? In a recent study, the presence of depressive symptoms ... in normally healthy individuals was found to correlate with rapid kidney function decline. ...
... low emotional function (OR, 0.725; 95% CI, 0.540-0.973; P = .032), low global quality of life (OR, 0.893; 95% CI, 0.812-0.983; ... Notably, the likelihood of depression in patients with cancer who experienced SAEs was greater than the likelihood of anxiety, ... Likelihood of Depression Is High in Patients With Cancer Who Experience Serious Adverse Events. October 17, 2023. Gillian ... lower cognitive function (OR, 0.907; 95% CI, 0.824-0.998; P = .046) and lower global quality of life (OR, 0.945; 95% CI, 0.898- ...
... Full Text (PDF, 620KB), ... Its proposed to use an approach based on membership and likelihood functions sharing. A number of performed experiments proved ... "Fuzzy Clustering Data Given on the Ordinal Scale Based on Membership and Likelihood Functions Sharing", International Journal ... 17]Dempster A. P., Laird N. M., and R. D. B., Maximum-Likelihood from Incomplete Data via the EM Algorithm // Journal of the ...
Lognormal function is applied for describing the life di ... Lognormal function is applied for describing the life ... Reliability Life Prediction of VFD by Constant Temperature Stress Accelerated Life Tests and Maximum Likelihood Estimation. ... Assuming an Arrhenius model, the lognormal parameters are computed by using the maximum likelihood estimation. Furthermore, a ...
likelihood-ratio test). b-d, Mean \(\beta \)-LFP phase in each cortical area (PRR \(\beta \)-LFP phase, y axis; LIP \(\beta \)- ... a-c, PRR firing rate and a function of dual-coherent \(\beta \)-LFP phase for each peri-reach (a), post-reach (b), and saccade ... likelihood-ratio test). e-g, \(\beta \)-LFP phase in PRR (y-axis) and LIP (x-axis, colorscale: proportion of trials). Downward ... 4 Negative-log-likelihood and generalization errors for model fits.. Second saccade reaction time: a, Dual-phase negative-log- ...
Mean-cyclic-error lower bounds via integral transform of likelihood-ratio function. / Nitzan, Eyal; Routtenberg, Tirza; ... Mean-cyclic-error lower bounds via integral transform of likelihood-ratio function. In 2016 IEEE Sensor Array and Multichannel ... Mean-cyclic-error lower bounds via integral transform of likelihood-ratio function. 2016 IEEE Sensor Array and Multichannel ... Dive into the research topics of Mean-cyclic-error lower bounds via integral transform of likelihood-ratio function. Together ...
Machnes Y. Production decisions in case of monotone likelihood ratio shifts of cumulative distribution functions. Insurance: ... Production decisions in case of monotone likelihood ratio shifts of cumulative distribution functions. / Machnes, Yaffa. In: ... Machnes, Y. (1993). Production decisions in case of monotone likelihood ratio shifts of cumulative distribution functions. ... Machnes, Y 1993, Production decisions in case of monotone likelihood ratio shifts of cumulative distribution functions, ...
Likelihood Function. Sign in. Sign in. Remember me Forgot username or password? , Create account ... Generality of Maximum Likelihood Least Squares Note that the maximum likelihood estimate coincides with the least squares ...
3. Likelihood function. On the full-sky, the distribution of auto-spectra is a scaled-χ2 with 2ℓ + 1 degrees of freedom. The ... free parameters in the full likelihood function (see Appendix B). We note that the Planck public likelihood depends on more ... We define several likelihood functions based on the information used: hlpT for TT cross-spectra, hlpE for EE cross-spectra, hlp ... 14) are less in tension with the Planck low-ℓ likelihoods. The HiLLiPOP only likelihoods give which is, for hlpT, at 1.7σ from ...
can be determined by maximizing the dual function . Next: Maximum likelihood Up: Maxent Modeling Previous: The maxent principle ... Define the dual function as and the dual optimization problem as Since and are fixed, the righthand side of (14) has only the ... Next: Maximum likelihood Up: Maxent Modeling Previous: The maxent principle Exponential form. The maximum entropy principle ...
Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user ... Wall Street traders have priced in a 30% likelihood of such a drastic move, according to the CME Group. Even if an economic ... Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ... the likelihood that the central bank can engineer a so-called "soft landing" appears to be dimming. With inflation at a four- ...
12.3 The Likelihood Function 216. 12.4 Longitudinal Data 221. 12.5 Regularizing the Likelihood 224. 12.6 Generalizations 232. ... Chapter 4: Likelihood Functions for Discrete State/Control Models 38. 4.1 Likelihood with Complete Observability 38. 4.2 ... 7.2 Likelihood: General Considerations 89. 7.3 Likelihood: Specifics for Wage Data 94. 7.3.1 Wage Data Alone--One Parameter 96 ... 7.4 Likelihood: Wage and Duration Data 100. 7.4.1 Wage and Duration Data--Two Parameters 100. 7.4.2 Wage and Duration Data-- ...

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