17. An Internet service provider has an online help service for its customers. Customer queries that take more than five minutes to resolve are categorized as “unsatisfactory”

experiences. To evaluate the quality of its service, the company takes 10 samples of 100 calls each while the process is under control. The resulting p values for unsatisfactory calls are as follows:

a. (**) Calculate the and Sp values, and set up control limits so that future sample p values should fall within the control limits 99.7% of the time.

b. (**) Suppose the Internet service provider in Part a takes four additional samples, yielding the following p values: 0.9, 0.12, 0.25, and 0.10. Plot the results and circle all values that suggest the process is “out of control.”
Is it possible that a sample result could fall outside of the control limits due to pure chance? Explain.

c. (**) Now suppose that the sample size is actually 50, not 100. Recalculate the control limits for the p chart.
What happened? Explain.

Transcribed Image Text:

P VALUES (n = 100) 0.08 0.11 0.12 0.06 0.13 0.09 0.16 0.09 0.18 0.15