Marketing analysts have determined that a particular advertising campaign should make at least 20% of the adult population aware of the advertised product. After a recent campaign, 400 adults were asked whether or not they had seen the ad and were aware of the new product.
a. What is the standard error of p¯?
b. What is the probability that the sample proportion will be less than 15%?
c. What is the probability that the sample proportion will be between 21.25% and 16.25%?
d. What is the probability that the sample proportion will be more than 22.5%?