What does validity refer to in measurement?

• A. The consistency of measurements across raters
• B. The accuracy of measurements in repeated trials
• C. The degree to which results can be generalized to other populations
• D. The degree to which an instrument measures what it is intended to measure

Answer: (D)

Validity refers to whether a measurement actually assesses the attribute it's meant to measure. It answers the question of whether the tool is capturing the intended construct rather than something else. This is different from reliability, which is about consistency: inter-rater reliability describes how well different evaluators agree, while test-retest reliability concerns consistency across repeated measurements. Generalizability, or external validity, relates to applying results to other populations. Those ideas are about consistency or applicability, not about whether the instrument measures the right thing. So the statement that best captures the concept is that validity is the degree to which an instrument measures what it is intended to measure.