Intratester reliability measures what?

• A. Consistency between different testers
• B. Consistency of measurements when the same tester repeats
• C. Validity of the instrument
• D. Reliability across different populations

Answer: (B)

Intratester reliability focuses on how consistent a single tester’s measurements are when they repeat the measurement on the same subject under the same conditions. It’s about repeatability and how much results vary from one attempt to another by the same person.

That’s why the statement describing consistency of measurements when the same tester repeats is the best fit. Intertester reliability would be about different testers agreeing with each other, which is a different concept. Validity is about whether the instrument measures what it’s intended to measure, not about repeated measurements by one tester. Reliability across different populations is not the standard way reliability is defined; reliability concerns consistency of measurements, not how they function across diverse groups.