If the upper and lower control limits are set at $\pm$3 standard deviations from the mean, we would expect that
A) 99.7% of the sample means are within the control limits
B) 95% of the sample means are within the control limits
C) about 68% of the sample means are within the control limits
D) about 5% of the sample means are outside the control limits

Question

If the upper and lower control limits are set at  $\pm$3 standard deviations from the mean, we would expect that
A) 99.7% of the sample means are within the control limits
B) 95% of the sample means are within the control limits
C) about 68% of the sample means are within the control limits
D) about 5% of the sample means are outside the control limits

Quizplus · Accepted Answer

Setting control limits at $\pm$3 standard deviations from the mean corresponds to the empirical rule, which states that 99.7% of data falls within three standard deviations in a normal distribution.

If the Upper and Lower Control Limits Are Set At \pm