validity(redirected from External validity)
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Correctness; especially the degree of closeness by which iterated results approach the correct result.
validitythe extent to which a measure, indicator or method of data collection possesses the quality of being sound or true as far as can be judged. For example, if a psychological measure, such as an intelligence test, is considered to be valid, this means that it is thought to measure what it sets out to measure. If social survey observations are said to have produced valid data, then they are considered to be true reflection of the phenomenon being studied in the population being studied (e.g. projections of voting behaviour), and the survey method could be said to have validity. Compare RELIABILITY.
In practice, in sociology and the social sciences generally, the relation between indicators and measures on the one hand and the underlying concepts they are taken to represent is often contested (see OFFICIAL STATISTICS, MEASUREMENT BY FIAT).