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Subgroup Analysis
Subgroup analysis refers to repeating the analysis of a study within subgroups of subjects defined by a subgrouping variable. For example: smoking status defining two subgroups: smokers and non-smokers. See also *Post hoc analysis In a scientific study, post hoc analysis (from Latin ''post hoc'', "after this") consists of statistical analyses that were specified after the data were seen. They are usually used to uncover specific differences between three or more group mean ... References Statistical analysis Design of experiments Medical statistics {{health-informatics-stub ...
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Analysis
Analysis (: analyses) is the process of breaking a complex topic or substance into smaller parts in order to gain a better understanding of it. The technique has been applied in the study of mathematics and logic since before Aristotle (384–322 BC), though ''analysis'' as a formal concept is a relatively recent development. The word comes from the Ancient Greek (''analysis'', "a breaking-up" or "an untying" from ''ana-'' "up, throughout" and ''lysis'' "a loosening"). From it also comes the word's plural, ''analyses''. As a formal concept, the method has variously been ascribed to René Descartes ('' Discourse on the Method''), and Galileo Galilei. It has also been ascribed to Isaac Newton, in the form of a practical method of physical discovery (which he did not name). The converse of analysis is synthesis: putting the pieces back together again in a new or different whole. Science and technology Chemistry The field of chemistry uses analysis in three ways: to i ...
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Subgroup
In group theory, a branch of mathematics, a subset of a group G is a subgroup of G if the members of that subset form a group with respect to the group operation in G. Formally, given a group (mathematics), group under a binary operation ∗, a subset of is called a subgroup of if also forms a group under the operation ∗. More precisely, is a subgroup of if the Restriction (mathematics), restriction of ∗ to is a group operation on . This is often denoted , read as " is a subgroup of ". The trivial subgroup of any group is the subgroup consisting of just the identity element. A proper subgroup of a group is a subgroup which is a subset, proper subset of (that is, ). This is often represented notationally by , read as " is a proper subgroup of ". Some authors also exclude the trivial group from being proper (that is, ). If is a subgroup of , then is sometimes called an overgroup of . The same definitions apply more generally when is an arbitrary se ...
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Smoking
Smoking is a practice in which a substance is combusted, and the resulting smoke is typically inhaled to be tasted and absorbed into the bloodstream of a person. Most commonly, the substance used is the dried leaves of the tobacco plant, which have been rolled with a small rectangle of paper into an elongated cylinder called a cigarette. Other forms of smoking include the use of a smoking pipe or a bong. Smoking is primarily practised as a route of administration for psychoactive chemicals because the active substances within the burnt dried plant leaves vaporize and can be airborne-delivered into the respiratory tract, where they are rapidly absorbed into the bloodstream of the lungs and then reach the central nervous system. In the case of tobacco smoking, these active substances are a mixture of aerosol particles that includes the pharmacologically active alkaloid nicotine, which stimulates the nicotinic acetylcholine receptors in the brain. Other notable active ...
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NEJM
''The New England Journal of Medicine'' (''NEJM'') is a weekly medical journal published by the Massachusetts Medical Society. Founded in 1812, the journal is among the most prestigious peer-reviewed medical journals. Its 2023 impact factor was 96.2, ranking it 2nd out of 168 journals in the category "Medicine, General & Internal". History In September 1811, Boston physician John Collins Warren, along with James Jackson, submitted a formal prospectus to establish the ''New England Journal of Medicine and Surgery and Collateral Branches of Science'' as a medical and philosophical journal. Subsequently, the first issue of the ''New England Journal of Medicine and Surgery and the Collateral Branches of Medical Science'' was published in January 1812. The journal was published quarterly. In 1823, another publication, the ''Boston Medical Intelligencer'', appeared under the editorship of Jerome V. C. Smith. The editors of the ''New England Journal of Medicine and Surgery and the Col ...
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Post Hoc Analysis
In a scientific study, post hoc analysis (from Latin ''post hoc'', "after this") consists of statistical analyses that were specified after the data were seen. They are usually used to uncover specific differences between three or more group means when an analysis of variance (ANOVA) test is significant. This typically creates a multiple testing problem because each potential analysis is effectively a statistical test. Multiple testing procedures are sometimes used to compensate, but that is often difficult or impossible to do precisely. Post hoc analysis that is conducted and interpreted without adequate consideration of this problem is sometimes called '' data dredging'' (''p''-hacking) by critics because the statistical associations that it finds are often spurious. Post hoc analyses are not inherently bad or good; rather, the main requirement for their ethical use is simply that their results not be mispresented as the original hypothesis. Modern editions of scientific manu ...
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Statistical Analysis
Statistical inference is the process of using data analysis to infer properties of an underlying probability distribution.Upton, G., Cook, I. (2008) ''Oxford Dictionary of Statistics'', OUP. . Inferential statistical analysis infers properties of a Statistical population, population, for example by testing hypotheses and deriving estimates. It is assumed that the observed data set is Sampling (statistics), sampled from a larger population. Inferential statistics can be contrasted with descriptive statistics. Descriptive statistics is solely concerned with properties of the observed data, and it does not rest on the assumption that the data come from a larger population. In machine learning, the term ''inference'' is sometimes used instead to mean "make a prediction, by evaluating an already trained model"; in this context inferring properties of the model is referred to as ''training'' or ''learning'' (rather than ''inference''), and using a model for prediction is referred to as ...
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Design Of Experiments
The design of experiments (DOE), also known as experiment design or experimental design, is the design of any task that aims to describe and explain the variation of information under conditions that are hypothesized to reflect the variation. The term is generally associated with experiments in which the design introduces conditions that directly affect the variation, but may also refer to the design of quasi-experiments, in which natural conditions that influence the variation are selected for observation. In its simplest form, an experiment aims at predicting the outcome by introducing a change of the preconditions, which is represented by one or more independent variables, also referred to as "input variables" or "predictor variables." The change in one or more independent variables is generally hypothesized to result in a change in one or more dependent variables, also referred to as "output variables" or "response variables." The experimental design may also identify ...
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