Reliability in testing. Which statement is true?

• A. Reliability refers to the consistency of a measurement across time and items.
• B. Reliability refers to the test's ability to measure what it intends to measure.
• C. Reliability guarantees external validity.
• D. Reliability means the test captures all aspects of the construct.

Answer: (A)

Reliability is about consistency of a measurement across time and items. A reliable test yields stable results if you administer it again later (test–retest reliability) and its items work together in a coherent way (internal consistency). This makes the score dependable and not overly influenced by random error.

That makes the statement describing consistency across time and items the best choice. The other ideas mix in validity—measuring what you intend to measure is validity, not reliability; reliability does not guarantee external validity (generalizability); and a test covering all aspects of a construct relates to content or construct validity rather than reliability. Remember, a measure can be reliable (consistent) but not valid (accurate about what you want to measure).