Which statement about the mean measurement of a shaft is true?

Which statement about the mean measurement of a shaft is true?

• A. The total sum of all measurements
• B. The smallest measurement observed
• C. The average of measurements taken at multiple points
• D. It is always equal to the nominal size

Answer: (C)

When assessing a shaft, you measure at several points along its length (and sometimes around its circumference) because the diameter can vary in different places. The mean measurement is the arithmetic average of those readings, giving a single representative size for the shaft. This makes it the best descriptor for overall size when you compare to the nominal value and its tolerance. For example, if you take five readings: 49.95, 50.00, 50.05, 49.98, and 50.02, the mean is (49.95 + 50.00 + 50.05 + 49.98 + 50.02) / 5 = 50.00. This average reflects the central size of the shaft, even though individual measurements vary. It’s not the total sum of measurements, which would just accumulate variation; it’s not the smallest measurement, which only shows the minimum size found; and it doesn’t have to be exactly equal to the nominal size due to manufacturing tolerances.

When assessing a shaft, you measure at several points along its length (and sometimes around its circumference) because the diameter can vary in different places. The mean measurement is the arithmetic average of those readings, giving a single representative size for the shaft. This makes it the best descriptor for overall size when you compare to the nominal value and its tolerance.

For example, if you take five readings: 49.95, 50.00, 50.05, 49.98, and 50.02, the mean is (49.95 + 50.00 + 50.05 + 49.98 + 50.02) / 5 = 50.00. This average reflects the central size of the shaft, even though individual measurements vary.

It’s not the total sum of measurements, which would just accumulate variation; it’s not the smallest measurement, which only shows the minimum size found; and it doesn’t have to be exactly equal to the nominal size due to manufacturing tolerances.