Managing for Quality and Performance Excellence 10th Edition by James Evans ,William Lindsay

Exercise 73

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.
River Bottom Fire Department (Prob. 8-22) determined that they needed to adjust their data-gathering process for response time to eliminate bias. The times were expected to fall within 3.8 and 5.3 minutes. After doing so, they wanted to evaluate the process to determine whether or not it was under control. Thirty new samples were taken on 30 random days from 6 stations. These data can be found in the worksheet Prob. 8-25 in the C08Data.xlsx file on the Student Companion Site for this chapter.
a. Compute the mean and range of each sample, calculate control limits, and plot them on x and R control charts.
b. Does the process appear to be in statistical control? Calculate descriptive statistics that may help you to determine the answer to this question. What evidence is there for your conclusion?