Which statistic is used to confirm precision?

• A. Mean
• B. SD and CV
• C. Range
• D. Median

Answer: (B)

Precision is about how consistently repeated measurements agree with each other. The standard deviation shows how spread out the repeated results are around the mean; a small SD means the results cluster tightly, which is the essence of good precision. The coefficient of variation expresses that spread as a percentage of the mean, so it lets you compare precision across different tests or concentration ranges. Together, SD and CV quantify how reproducible a measurement is. The mean and median describe central value, not how tightly results are grouped, while the range only captures the outer spread and can be heavily affected by outliers, making it a poor stand-alone measure of precision. In practice, you assess precision by looking at SD and CV across repeated measurements of a control sample.