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

Exercise 20

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.
Charlie Plato owns Charlie's China Emporium, which sells inexpensive cups, dishes, and bric-a-brac in a seaside resort. She has three checkout stations, which she would like to test to see if they are under control and capable. She estimates sales of $36.50 per hour, per station, to be a representative average. Consider the data for 75 individual results of sales dollars per hour, per unit, shown in the worksheet Prob. 8-39 in the C08Data.xlsx file.
a. Compute control limits for an x -chart (chart for individuals) using the statistic
as an estimate of the standard deviation with a 3-period moving range.
b. Construct an x -chart for individuals, using the data. Interpret the results.