Which statement best defines reliability in survey instruments?

• A. Reliability refers to consistency across time and items.
• B. Validity means measurements are always precise to three decimals.
• C. Reliability ensures no bias in the measurement instrument.
• D. Validity is about sampling method only.

Answer: (A)

Reliability is about consistency and repeatability of a measurement. In survey instruments, this means that if the same person were surveyed under similar conditions at different times, the scores would be similar (test-retest reliability), and if the instrument includes multiple items intended to measure the same construct, those items would yield similar results (internal consistency). This focus on stable, repeatable results is what reliability captures.

The other ideas mix in different concepts. Precision to a fixed decimal place isn’t what reliability measures—it's not about how many decimals the measurement shows. Reliability also doesn’t guarantee that the instrument is measuring what it should measure; that’s validity. An instrument can be highly reliable (giving consistent results) but still be invalid if it’s not actually measuring the intended construct. Plus, validity involves broader considerations, including sampling and how well the instrument generalizes, not just consistency.