Which definition best describes reliability?

Which definition best describes reliability?

• A. Consistency of a measure across time or observers.
• B. The degree to which a measure predicts future outcomes.
• C. The degree to which a measure captures the theoretical construct.
• D. The extent to which measure results align with other established measures.

Answer: (A)

Reliability is about consistency in measurement. A measurement is reliable when it yields similar results under the same conditions—for example, if you administer it to the same person at different times, the scores stay close, or if different observers rate the same behavior, their scores align. This focus on stability and agreement across time or raters is what reliability captures. The other ideas describe validity: a measure that predicts future outcomes reflects predictive validity; a measure that captures the intended theoretical construct reflects construct validity; and a measure that agrees with other established measures reflects convergent or criterion validity. But reliability specifically targets consistency, not necessarily whether the measure is measuring what it’s supposed to measure.

Reliability is about consistency in measurement. A measurement is reliable when it yields similar results under the same conditions—for example, if you administer it to the same person at different times, the scores stay close, or if different observers rate the same behavior, their scores align. This focus on stability and agreement across time or raters is what reliability captures.

The other ideas describe validity: a measure that predicts future outcomes reflects predictive validity; a measure that captures the intended theoretical construct reflects construct validity; and a measure that agrees with other established measures reflects convergent or criterion validity. But reliability specifically targets consistency, not necessarily whether the measure is measuring what it’s supposed to measure.