Selection bias is the error introduced when the individuals, groups or data selected for analysis are not representative of the population intended to be analyzed, because the selection process itself is not random. It can arise in many forms, including sampling bias, in which a survey systematically over- or under-represents certain groups, and self-selection bias, in which the people who choose to participate in a study differ systematically from those who do not. Selection bias is a central methodological concern across the sciences because it can produce conclusions that appear statistically sound within the biased sample but do not generalize to the broader population the researcher actually intended to study, and survivorship bias is one commonly cited special case of it.
Facts
Core ClaimThe bias typically arises when a study conditions on a factor that is itself shaped by both the exposure and the outcome under study, manufacturing an association between the two that does not exist in the eligible population as a whole. 1 Classification
Type of Phenomenon Sources
1. Wikipedia: Selection bias
Wikimedia Foundationlead paragraph, definition
Selection bias is the bias introduced by the selection of individuals, groups, or data for analysis in such a way that the association between exposure and outcome among those selected for analysis differs from the association among those eligible.
lead section, defining sentence
Selection bias is the bias introduced by the selection of individuals, groups, or data for analysis in such a way that the association between exposure and outcome among those selected for analysis differs from the association among those eligible.
lead section, phenomenon-kind classification
Selection bias is the bias introduced by the selection of individuals, groups, or data for analysis in such a way that the association between exposure and outcome among those selected for analysis differs from the association among those eligible.
In Group: Selection and Sampling Biases, Lead
Selection bias is the bias introduced by the selection of individuals, groups, or data for analysis in such a way that the association between exposure and outcome among those selected for analysis differs from the association among those eligible.
View the Source Catalogue of Bias: Selection bias
definition, opening sentenceQuote, definition, opening sentence
occurs when individuals or groups in a study differ systematically from the population of interest leading to a systematic error in an association or outcome.
NCBI Bookshelf: Statistical Methods in Cancer Research, Selection Bias and Other Miscellaneous Biases
Section 5.1, IntroductionQuote, Section 5.1, Introduction
Selection bias is present when the effect estimate (e.g. the odds ratio [OR]) of the association between the exposure and the outcome in the study population is different from that in the source population, because of selective recruitment into the study or selective loss to follow-up.
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