You want to determine the control lines for a p-chart for quality control purposes. If the desired confidence level is 99 percent, which of the following values for "z" would you use in computing the UCL and LCL?
A) 0.99
B) 2
C) 2.58
D) 3
E) None of these choices are correct.

Question

Quizplus · Accepted Answer

To determine the control lines for a p-chart with a 99% confidence level, we need to use a z-value that corresponds to the 99.5th percentile of the standard normal distribution (since we need to divide the alpha level of 0.01 equally between the two tails of the distribution). This value is 2.58. Therefore, we would use a value of 2.58 in computing the UCL and LCL.

You Want to Determine the Control Lines for a P-Chart