A 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 the sample size was 25 (other factors remain unchanged), the interval forwould: a. become wider b. become zero c. not change d. become narrower