For Exercises 49–56, do the following:
55. Americans' Height. A random sample of 400 American adults yields a mean height of 176 centimeters. Assume . Conduct a hypothesis test to investigate whether the population mean height of American adults has changed from 175 centimeters, using level of significance .
9.2.55
(a) (b) . Reject if or if . (c) .
(d) Since is , the conclusion is reject . There is evidence at the 0.10 level of significance that the population mean height of Americans has changed from 175 centimeters.