Which statement correctly defines accuracy in laboratory measurement?

• A. Accuracy is the ability to give a true measure of the chemical.
• B. Precision relates to the consistency of the results.
• C. Repeatability refers to variability among results from different laboratories.
• D. Reliability is the ability of a test to distinguish between individuals.

Answer: (A)

Accuracy is about how close a measurement is to the true value of what you’re trying to measure. The statement that best defines accuracy says it reflects the ability to give a true measure of the chemical. In practice, if the true concentration is X, measurements near X are accurate; measurements that miss X by a lot are less accurate.

It helps to contrast with precision: precision refers to how consistently measurements cluster together, regardless of whether they are near the true value. You can be precise but not accurate if your results are tightly grouped but far from the true value. Repeatability is a form of precision measured under the same conditions (same method, same operator, same instrument) over a short time; stating that repeatability involves results from different laboratories would mix up reproducibility, which is precision across different labs. Reliability in this context would describe the ability to distinguish between individuals, which is more about diagnostic validity than how close a measurement is to the true value.