Which statement correctly describes the relationship between reliability and validity?

• A. Reliability is the accuracy of a measure; validity is the consistency of measurement
• B. Reliability and validity are unrelated concepts
• C. Reliability is a prerequisite for validity; a valid test must be reliable
• D. A test with high validity always has high reliability

Answer: (C)

Reliability means the scores are consistent across repeated measurements, items, or raters. Validity means the test actually measures the intended construct and relates to relevant outcomes. A prerequisite for validity is reliability: if a measure is not reliable, its scores are too noisy to support a meaningful claim about the construct, so it cannot be valid. For example, a bathroom scale that fluctuates from weigh-in to weigh-in is reliable only if those fluctuations are tiny and predictable; if the readings are inconsistent, you can’t trust it to reflect true weight, so validity is compromised. It's possible to have a measure that is reliable but not valid (consistently measuring something else), but a valid measure cannot be truly valid unless its reliability is at least adequate. This is why reliability is described as a prerequisite for validity.