Like any other large firm, Thorndike Sports Equipment receives daily telephone calls in which customers either praise or complain about a Thorndike product. Luke Thorndike is especially sensitive about the number of complaint calls received daily. Twelve weeks ago, he asked the customer service department to keep a daily log of the number of telephoned complaints received each day. Just six weeks ago, Thorndike ads began carrying a toll-free number through which customers could inquire or comment about Thorndike products.
1. Assuming the daily number of calls to be Poisson distributed, construct a c-chart for the first 30 days.
Using 3-sigma limits, were there any days in which the volume of complaints fell outside the limits?
2. If any unusually high or low days were identified in part 1, construct a new pair of 3-sigma limits based on the days that remain from the initial 30-day period.
3. Using the upper and lower limits identified in part 2, extend the c-chart to include days 31€“60. Based on the 3-sigma limits in this chart, does it appear that the toll-free number has caused a shift in the daily number of complaints received?

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