The term applied to a test that measures what it is intended to measure.
The degree to which data or results of a study are correct or true; the extent to which a situation as observed reflects the true situation.
The fact of being based on sound research and methods which exclude alternative explanations of a result.
In relation to tests, the extent to which a test actually measures what it sets out to measure, and so the extent to which it is actually useful or meaningful to use the test results. In educational testing, this is of special concern to parents and a highly controversial question. In intelligence tests, for example, it is unclear precisely what is being tested, for no one knows for sure what intelligence is and whether and how it would be possible to test it.
An indication of the extent to which a clinical sign or test is a true indicator of disease. Reduced validity can arise if the tests produce different results when conducted several times on the same person under identical conditions (i.e. reduced reproducibility, reliability, or repeatability). This may be because the same observer gets different results on successive occasions (intraobserver error) or because a series of different observers fail to obtain the same result (interobserver error). Such errors may arise because of a true difference in observation and/or interpretation or because of a preconceived notion (often unconscious) by the observer, which influences either his judgment or the tone and manner with which he questions the patient.
The degree to which data or results of a study are correct or true.
Measurement validity pertains to the extent to which a test accurately assesses what it intends to measure. It reflects the degree to which the test aligns with its stated purpose and effectively captures the targeted construct or attribute.