What term describes the range that controls should fall within to ensure accuracy (Mean ± 2SD)?

• A. Precision
• B. Control Range
• C. Imprecision
• D. Inaccuracy

Answer: (B)

In quality control, the term describes the allowable span for control measurements to indicate the system is performing properly. This range is defined by the mean plus or minus two standard deviations, which captures about 95% of expected control results if the data are normally distributed. Keeping control results within this boundary helps ensure the measurement system is accurate and stable over time.

Other terms describe quality attributes rather than the acceptable span for controls. Precision refers to how repeatable measurements are, not the acceptable range a control result should fall within. Imprecision is the lack of precision. Inaccuracy means bias or a systematic error from the true value.