A worldwide rental car company receives about 10,000 customer complaint calls per month at its European call center. In an effort to reduce the proportion of issues that are not resolved on the customer's first call, management conducted a thorough study of the call center's procedures. The results were published in the International Journal of Productivity and Performance Management (Vol. 59, 2010). After making major changes at the call center, management constructed a p-chart to monitor the process improvements. Assume that 18 calls to the center were sampled each day for 60 consecutive days. The article reported that the proportion of all calls in the sample that had unresolved issues at the end of the call was .107. (This was a major improvement over the previous unresolved-first-call rate of .845.)
a. What is the centerline for the p-chart?
b. Compute the lower and upper control limits for the p-chart.
c. When the proportions of daily calls that resulted in unresolved issues are plotted on the p-chart, all fall within the LCL and UCL boundaries. What does this imply about the process?