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Post Hoc Comparison
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 manua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Latin Language
Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area around Rome, Italy. Through the expansion of the Roman Republic, it became the dominant language in the Italian Peninsula and subsequently throughout the Roman Empire. It has greatly influenced many languages, Latin influence in English, including English, having contributed List of Latin words with English derivatives, many words to the English lexicon, particularly after the Christianity in Anglo-Saxon England, Christianization of the Anglo-Saxons and the Norman Conquest. Latin Root (linguistics), roots appear frequently in the technical vocabulary used by fields such as theology, List of Latin and Greek words commonly used in systematic names, the sciences, List of medical roots, suffixes and prefixes, medicine, and List of Latin legal terms ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiple Comparisons
Multiple comparisons, multiplicity or multiple testing problem occurs in statistics when one considers a set of statistical inferences simultaneously or estimates a subset of parameters selected based on the observed values. The larger the number of inferences made, the more likely erroneous inferences become. Several statistical techniques have been developed to address this problem, for example, by requiring a stricter significance threshold for individual comparisons, so as to compensate for the number of inferences being made. Methods for family-wise error rate give the probability of false positives resulting from the multiple comparisons problem. History The problem of multiple comparisons received increased attention in the 1950s with the work of statisticians such as Tukey and Scheffé. Over the ensuing decades, many procedures were developed to address the problem. In 1996, the first international conference on multiple comparison procedures took place in Tel Aviv. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Analysis
Data analysis is the process of inspecting, Data cleansing, cleansing, Data transformation, transforming, and Data modeling, modeling data with the goal of discovering useful information, informing conclusions, and supporting decision-making. Data analysis has multiple facets and approaches, encompassing diverse techniques under a variety of names, and is used in different business, science, and social science domains. In today's business world, data analysis plays a role in making decisions more scientific and helping businesses operate more effectively. Data mining is a particular data analysis technique that focuses on statistical modeling and knowledge discovery for predictive rather than purely descriptive purposes, while business intelligence covers data analysis that relies heavily on aggregation, focusing mainly on business information. In statistical applications, data analysis can be divided into descriptive statistics, exploratory data analysis (EDA), and Statistical h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Outcome Switching
Outcome switching is the practice of changing the primary or secondary outcomes of a clinical trial after its initiation. An outcome is the goal of the clinical trial, such as survival after five years for cancer treatment. Outcome switching can lead to bias and undermine the reliability of the trial, for instance when outcomes are switched after researchers already have access to trial data. That way, researchers can cherry pick an outcome which is statistically significant. Problem Outcome switching can undermine the reliability of the trial, for instance when outcomes are switched when researchers already have access to the trial data. It can lead to bias in terms of benefits and harms. For example, when the findings using the original protocol were statistically insignificant, a study may cherry pick a new outcome measure that is statistically significant. If there are a large number of outcomes to choose from, it is likely at least one will show significant findings, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Testing Hypotheses Suggested By The Data
In statistics, hypotheses suggested by a given dataset, when tested with the same dataset that suggested them, are likely to be accepted even when they are not true. This is because circular reasoning (double dipping) would be involved: something seems true in the limited data set; therefore we hypothesize that it is true in general; therefore we wrongly test it on the same, limited data set, which seems to confirm that it is true. Generating hypotheses based on data already observed, in the absence of testing them on new data, is referred to as ''post hoc'' theorizing (from Latin language, Latin ''post hoc analysis, post hoc'', "after this"). The correct procedure is to test any hypothesis on a data set that was not used to generate the hypothesis. The general problem Testing a hypothesis suggested by the data can very easily result in false positives (type I errors). If one looks long enough and in enough different places, eventually data can be found to support any hypothes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HARKing
HARKing (hypothesizing after the results are known) is an acronym coined by social psychologist Norbert Kerr that refers to the questionable research practice of "presenting a post hoc hypothesis in the introduction of a research report as if it were an a priori hypothesis". Hence, a key characteristic of HARKing is that post hoc hypothesizing is falsely portrayed as a priori hypothesizing. HARKing may occur when a researcher tests an a priori hypothesis but then omits that hypothesis from their research report after they find out the results of their test. Post hoc analysis or post hoc theorizing then may lead to a post hoc hypothesis. Types Several types of HARKing have been distinguished, including: ;THARKing: Transparently hypothesizing after the results are known, rather than the secretive, undisclosed, HARKing that was first proposed by Kerr. In this case, researchers openly declare that they developed their hypotheses after they observed their research results. ;CHARKing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tukey's Range Test
Tukey's range test, also known as Tukey's test, Tukey method, Tukey's honest significance test, or Tukey's HSD (honestly significant difference) test, : Also occasionally described as "honestly", see e.g. is a single-step multiple comparison procedure and statistical test. It can be used to correctly interpret the statistical significance of the difference between means that have been selected for comparison because of their extreme values. The method was initially developed and introduced by John Tukey for use in Analysis of Variance (ANOVA), and usually has only been taught in connection with ANOVA. However, the studentized range distribution used to determine the level of significance of the differences considered in Tukey's test has vastly broader application: It is useful for researchers who have searched their collected data for remarkable differences between groups, but then cannot validly determine how significant their discovered stand-out difference is using standar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scheffé's Method
In statistics, Scheffé's method, named after American statistician Henry Scheffé, is a method for adjusting significance levels in a linear regression analysis to account for multiple comparisons. It is particularly useful in analysis of variance (a special case of regression analysis), and in constructing simultaneous confidence bands for regressions involving basis functions. Scheffé's method is a single-step multiple comparison procedure which applies to the set of estimates of all possible contrasts among the factor level means, not just the pairwise differences considered by the Tukey–Kramer method. It works on similar principles as the Working–Hotelling procedure for estimating mean responses in regression, which applies to the set of all possible factor levels. The method Let \mu_1, \ldots , \mu_r be the mean A mean is a quantity representing the "center" of a collection of numbers and is intermediate to the extreme values of the set of numbers. There a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Post Hoc (other)
''Post hoc'' (sometimes written as ''post-hoc'') is a Latin phrase, meaning "after this" or "after the event". ''Post hoc'' may refer to: * ''Post hoc'' analysis or ''post hoc'' test, statistical analyses that were not specified before the data were seen * ''Post hoc'' theorizing, generating hypotheses based on data already observed *''Post hoc ergo propter hoc'' (after this, therefore because of this), a logical fallacy of causation * "Post Hoc, Ergo Propter Hoc" (''The West Wing''), an episode of the television series ''The West Wing'' See also * ''Propter hoc'' (other) * ''A priori'' and ''a posteriori'', Latin phrases used in philosophy meaning "from earlier" and "from later" *''Ex post'', Latin phrase meaning "after the event" *''Ad hoc ''Ad hoc'' is a List of Latin phrases, Latin phrase meaning literally for this. In English language, English, it typically signifies a solution designed for a specific purpose, problem, or task rather than a Generalization, ge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
