Exhibit 8-3 A random sample of 81 automobiles traveling on a section of an interstate showed an average speed of 60 mph.

Exhibit 8-3A random sample of 81 automobiles traveling on a section of an interstate showed an average speed of 60 mph. The distribution of speeds of all cars on this section of highway is normally distributed, with a standard deviation of 13.5 mph.Refer to Exhibit 8-3. If we are interested in determining an interval estimate for m at 86.9% confidence, the z value to use is