According to the text, the most common choice of limits for control charts is usually
A) ± 1 standard deviation.
B) ± 2 standard deviations.
C) ± 3 standard deviations.
D) ± 3 standard deviations for means and ± 2 standard deviations for ranges.
E) ± 1 standard deviations for means and ± 2 standard deviations for ranges.

Question

Quizplus · Accepted Answer

The most common choice for control chart limits is ± 3 standard deviations, as this captures 99.73% of the data if the underlying distribution is normal. This provides a practical balance between detecting meaningful changes in process performance while minimizing false alarms. Other choices (such as ± 2 standard deviations) are less sensitive to changes in process performance, while choices that vary between mean and range limits can be more difficult to use effectively.

According to the Text, the Most Common Choice of Limits