A sample of 40 CDs from a student's collection showed a mean length of 52.74 minutes with

Question:

A sample of 40 CDs from a student's collection showed a mean length of 52.74 minutes with a standard deviation of 13.21 minutes. Construct a 95 percent confidence interval for the population standard deviation. (Data are from a project by statistics students Michael Evatz, Nancy Petack, and Jennifer Skladanowski.)