Managing for Quality and Performance Excellence 9th Edition by James Evans,William Lindsay

Exercise 15

Note: Data for many of the problems in this chapter can be found in the Excel workbook C08Data.xlsx on the Student Companion Site. Click on the appropriate worksheet tab as noted in the problem (e.g., Prob. 8-6, etc.) to access the data.
Chief Henry Batter of the Gotham City Police Department is trying to reduce the time required to answer the phone at police headquarters (in fractions of a minute). The data in the worksheet for Prob. 8-38 in the C08Data.xlsx file on the Student Companion Site for this chapter represent time in fractions of minutes for three individual readings taken at random for 25 days.
a. Compute control limits for an x -chart (chart for individuals) using the statistic
with a 3-period moving range, as an estimate of the standard deviation.
b. Construct an x -chart for individuals, using the data. Interpret the results.