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

Exercise 40

Note: Data sets for many problems in this chapter are available in the Excel workbook C06Data.xlsx on the Student Companion Site. Click on the appropriate worksheet tab as noted in the problem (e.g., Prob. 6-1) to access the data. In addition, the spreadsheet templates illustrated in the chapter are also available to aid in solving many of these problems.
The mean time to pour and process 5 cubic yards of concrete by the Piedra Cretebuilders Co. is 15.5 minutes. If 2 percent of the projects with 5 yards of concrete require more than 15.75 minutes, what is the standard deviation of the time for such projects?