Reliability in psychological measurement is best defined as

• A. Accuracy of measurement
• B. Consistency of measurement
• C. Ability to predict outcomes
• D. Absence of measurement error

Answer: (B)

Reliability is about consistency. A measurement is reliable if it yields similar results under the same conditions, showing stability across time (test-retest), across raters, or among items that measure the same construct. This focus on repeatable, dependable scores is what makes reliability about consistency rather than perfect accuracy.

That’s why consistency of measurement is the best descriptor. The other ideas touch on related concepts but aren’t the core of reliability: accuracy of measurement aligns more with validity, the ability to predict outcomes is about predictive validity, and in practice there’s usually some measurement error even in reliable instruments, so “absence of measurement error” is too strong.