In a random sample of 100 viewers, 72% had a favorable impression of a new TV ad campaign.

a) Test the hypothesis that fewer than 80% of the population of all viewers have a favorable view of the ad campaign. Use the 0.05 level of significance. Explain your conclusion.

b) Construct a 95% confidence interval for the proportion of the population of all viewers who have a favorable view of the ad campaign. Interpret your results.