Which statement best distinguishes reliability and validity in psychological measurement?

• A. Reliability means consistency; validity means measuring the intended construct.
• B. Reliability means accuracy; validity means speed.
• C. Reliability and validity are unrelated.
• D. Reliability is about consistency; validity is about whether the measure assesses the intended construct.

Answer: (D)

Reliability is about consistency in measurement. It means the test yields stable results across repeated administrations, across items that hang together, or across raters who score it similarly. Validity, on the other hand, is about accuracy in what you’re claiming to measure—whether the scores actually reflect the construct you intend to assess.

The best way to phrase it is that reliability concerns consistency, while validity concerns whether the measure assesses the intended construct. A test can be reliable but not valid if it produces consistent scores that don’t really reflect the target construct. Conversely, validity relies on reliability because unstable scores undermine any claim of measuring the right thing. Some other statements mix up terms (for example, equating reliability with accuracy or speed, or claiming reliability and validity are unrelated), but those ideas miss the accepted distinction that consistency underpins reliability and the accuracy of the construct being measured underpins validity.