Recall that the cigarette industry requires that models in cigarette ads must appear to be at least 25 years old. Also recall that a sample of 50 people is randomly selected at a shopping mall. Each person in the sample is shown a "typical cigarette ad" and is asked to estimate the age of the model in the ad.

a: Let μ be the mean perceived age estimate for all viewers of the ad, and suppose we consider the industry requirement to be met if μ is at least 25. Set up the null and alternative hypotheses needed to attempt to show that the industry requirement is not being met.

b: Suppose that a random sample of 50 perceived age estimates gives a mean of 23.663 years and a standard deviation of s = 3.596 years. Use these sample data and critical values to test the hypotheses of part α at the .10, .05, .01, and .001 levels of significance.

c: How much evidence do we have that the industry requirement is not being met?

d: Do you think that this result has practical importance? Explain your opinion.