How is accuracy defined?

• A. Reproducibility of repeated measurements
• B. Closeness to true value
• C. Average of repeated measurements
• D. Measurement of instrument drift

Answer: (B)

Accuracy is the closeness of a measured value to the true value. It reflects bias in the measurement process and depends on proper calibration and using a valid reference standard. You’re accurate when your result matches the true value within acceptable limits.

Precision is about reproducibility—how tightly repeated measurements agree with each other. You can be very precise but not accurate if those consistent results are far from the true value.

Relying on the average of repeated measurements can improve an estimate, but it doesn’t define accuracy by itself, especially if there is systematic bias. Instrument drift refers to changes in measurements over time, which can affect accuracy but is not the definition of accuracy itself.