Root mean square expresses the ______ of point measurements.

• A. accuracy
• B. precision
• C. closeness
• D. refinement

Answer: (B)

Root mean square expresses the spread of the point measurements, reflecting how tightly the measurements cluster and how repeatable they are. This is a statement about precision—the consistency among repeated measurements. RMS essentially tracks the deviations from the central value (often the mean); a smaller RMS means the measurements are more tightly grouped, indicating higher precision. Accuracy, on the other hand, is about how close the average of the measurements is to the true value, which RMS does not directly measure. Closeness and refinement aren’t standard terms used to describe the variability of repeated measurements. So the best fit is precision.