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Matching (statistics)
Matching is a statistical technique that evaluates the effect of a treatment by comparing the treated and the non-treated units in an observational study or quasi-experiment (i.e. when the treatment is not randomly assigned). The goal of matching is to reduce bias for the estimated treatment effect in an observational-data study, by finding, for every treated unit, one (or more) non-treated unit(s) with similar observable characteristics against which the covariates are balanced out (similar to the K-nearest neighbors algorithm). By matching treated units to similar non-treated units, matching enables a comparison of outcomes among treated and non-treated units to estimate the effect of the treatment reducing bias due to confounding. Propensity score matching, an early matching technique, was developed as part of the Rubin causal model, but has been shown to increase model dependence, bias, inefficiency, and power and is no longer recommended compared to other matching methods. A si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Observational Study
In fields such as epidemiology, social sciences, psychology and statistics, an observational study draws inferences from a sample (statistics), sample to a statistical population, population where the dependent and independent variables, independent variable is not under the Scientific control, control of the researcher because of ethical concerns or logistical constraints. One common observational study is about the possible effect of a treatment on subjects, where the assignment of subjects into a treated group versus a control group is outside the control of the investigator. This is in contrast with experiments, such as randomized controlled trials, where each subject is Random assignment, randomly assigned to a treated group or a control group. Observational studies, for lacking an assignment mechanism, naturally present difficulties for inferential analysis. Motivation The independent variable may be beyond the control of the investigator for a variety of reasons: * A rand ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sociology
Sociology is the scientific study of human society that focuses on society, human social behavior, patterns of Interpersonal ties, social relationships, social interaction, and aspects of culture associated with everyday life. The term sociology was coined in the late 18th century to describe the scientific study of society. Regarded as a part of both the social sciences and humanities, sociology uses various methods of Empirical research, empirical investigation and critical analysis to develop a body of knowledge about social order and social change. Sociological subject matter ranges from Microsociology, micro-level analyses of individual interaction and agency (sociology), agency to Macrosociology, macro-level analyses of social systems and social structure. Applied sociological research may be applied directly to social policy and welfare, whereas Theory, theoretical approaches may focus on the understanding of social processes and phenomenology (sociology), phenomenologic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
External Validity
External validity is the validity of applying the conclusions of a scientific study outside the context of that study. In other words, it is the extent to which the results of a study can generalize or transport to other situations, people, stimuli, and times.Aronson, E., Wilson, T. D., Akert, R. M., & Fehr, B. (2007). Social psychology. (4 ed.). Toronto, ON: Pearson Education. Generalizability refers to the applicability of a predefined sample to a broader population while transportability refers to the applicability of one sample to another target population. In contrast, internal validity is the validity of conclusions drawn ''within'' the context of a particular study. Mathematical analysis of external validity concerns a determination of whether generalization across heterogeneous populations is feasible, and devising statistical and computational methods that produce valid generalizations. In establishing external validity, scholars tend to identify the "scope" of the study ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sampling Bias
In statistics, sampling bias is a bias (statistics), bias in which a sample is collected in such a way that some members of the intended statistical population, population have a lower or higher sampling probability than others. It results in a biased sample of a population (or non-human factors) in which all individuals, or instances, were not equally likely to have been selected. If this is not accounted for, results can be erroneously attributed to the phenomenon under study rather than to the method of sampling (statistics), sampling. Medical sources sometimes refer to sampling bias as ascertainment bias. Ascertainment bias has basically the same definition, but is still sometimes classified as a separate type of bias. Distinction from selection bias Sampling bias is usually classified as a subtype of selection bias, sometimes specifically termed sample selection bias, but some classify it as a separate type of bias. A distinction, albeit not universally accepted, of samplin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
In Vitro Fertilization
In vitro fertilisation (IVF) is a process of fertilisation in which an egg is combined with sperm in vitro ("in glass"). The process involves monitoring and stimulating the ovulatory process, then removing an ovum or ova (egg or eggs) from the ovaries and enabling sperm to fertilise them in a culture medium in a laboratory. After a fertilised egg (zygote) undergoes embryo culture for 2–6 days, it is transferred by catheter into the uterus, with the intention of establishing a successful pregnancy. IVF is a type of assisted reproductive technology used to treat infertility, enable gestational surrogacy, and, in combination with pre-implantation genetic testing, avoid the transmission of abnormal genetic conditions. When a fertilised egg from egg and sperm donors implants in the uterus of a genetically unrelated surrogate, the resulting child is also genetically unrelated to the surrogate. Some countries have banned or otherwise regulated the availability of IVF treatme ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perinatal Mortality
Perinatal mortality (PNM) is the death of a fetus or neonate and is the basis to calculate the perinatal mortality rate. ''Perinatal'' means "relating to the period starting a few weeks before birth and including the birth and a few weeks after birth." Variations in the precise definition of the perinatal mortality exist, specifically concerning the issue of inclusion or exclusion of early fetal and late neonatal fatalities. The World Health Organization defines perinatal mortality as the "number of stillbirths and deaths in the first week of life per 1,000 total births, the perinatal period commences at 22 completed weeks (154 days) of gestation, and ends seven completed days after birth", but other definitions have been used. The UK figure is about 8 per 1,000 and varies markedly by social class with the highest rates seen in Asian women. Globally, an estimated 2.6 million neonates died in 2013 before the first month of age down from 4.5 million in 1990. Causes Preterm birth i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiple Birth
A multiple birth is the culmination of a multiple pregnancy, wherein the mother gives birth to two or more babies. A term most applicable to vertebrate species, multiple births occur in most kinds of mammals, with varying frequencies. Such births are often named according to the number of offspring, as in ''twins'' and ''triplets''. In non-humans, the whole group may also be referred to as a ''litter'', and multiple births may be more common than single births. Multiple births in humans are the exception and can be exceptionally rare in the largest mammals. A multiple pregnancy may be the result of the fertilization of a single egg that then splits to create identical fetuses, or it may be the result of the fertilization of multiple eggs that create fraternal ("non-identical") fetuses, or it may be a combination of these factors. A multiple pregnancy from a single zygote is called '' monozygotic'', from two zygotes is called '' dizygotic'', or from three or more zygotes is called ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
British Medical Journal
''The BMJ'' is a fortnightly peer-reviewed medical journal, published by BMJ Publishing Group Ltd, which in turn is wholly-owned by the British Medical Association (BMA). ''The BMJ'' has editorial freedom from the BMA. It is one of the world's oldest general medical journals. Previously called the ''British Medical Journal'', the title was officially shortened to ''BMJ'' in 1988, and then changed to ''The BMJ'' in 2014. The current editor-in-chief of ''The BMJ'' is Kamran Abbasi, who was appointed in January 2022. History The journal began publishing on 3 October 1840 as the ''Provincial Medical and Surgical Journal'' and quickly attracted the attention of physicians around the world through its publication of high-quality original research articles and unique case reports. The ''BMJ''s first editors were P. Hennis Green, lecturer on the diseases of children at the Hunterian School of Medicine, who also was its founder, and Robert Streeten of Worcester, a member of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Statistical Bias
In the field of statistics, bias is a systematic tendency in which the methods used to gather data and estimate a sample statistic present an inaccurate, skewed or distorted (''biased'') depiction of reality. Statistical bias exists in numerous stages of the data collection and analysis process, including: the source of the data, the methods used to collect the data, the estimator chosen, and the methods used to analyze the data. Data analysts can take various measures at each stage of the process to reduce the impact of statistical bias in their work. Understanding the source of statistical bias can help to assess whether the observed results are close to actuality. Issues of statistical bias has been argued to be closely linked to issues of statistical validity. Statistical bias can have significant real world implications as data is used to inform decision making across a wide variety of processes in society. Data is used to inform lawmaking, industry regulation, corpor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Average Treatment Effect
The average treatment effect (ATE) is a measure used to compare treatments (or interventions) in randomized experiments, evaluation of policy interventions, and medical trials. The ATE measures the difference in mean (average) outcomes between units assigned to the treatment and units assigned to the control. In a randomized trial (i.e., an experimental study), the average treatment effect can be estimated from a sample using a comparison in mean outcomes for treated and untreated units. However, the ATE is generally understood as a causal parameter (i.e., an estimate or property of a population) that a researcher desires to know, defined without reference to the study design or estimation procedure. Both observational studies and experimental study designs with random assignment may enable one to estimate an ATE in a variety of ways. The average treatment effect is under some conditions directly related to the partial dependence plot. General definition Originating from e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
