A survey of 300 U.S. online shoppers was conducted. In response to the question of what would influence the shopper to spend more money online in 2012, 18% said free shipping, 13% said offered discounts while shopping, and 9% said product reviews. (Data extracted from "2012 Consumer Shopping Trends and Insights," Steel house, Inc., 2012.) Construct a 95% confidence interval estimate of the population proportion of online shoppers who would be influenced to spend more money online in 2012 with
a. Free shipping.
b. Offered discounts while shopping.
c. Product reviews.
d. You have been asked to update the results of this study. Determine the sample size necessary to estimate, with 95% confidence, the population proportions in (a) through (c) to within ±0.02.