To determine the effectiveness of the advertising campaign for a new DVD player, management would like to know what percentage of the households are aware of the new brand. The advertising agency thinks that this figure is as high as 70 percent. The management would like a 95 percent confidence interval and a margin of error no greater than plus or minus 2 percent.
a. What sample size should be used for this study?
b. Suppose that management wanted to be 99 percent confident but could tolerate an error of plus or minus 3 percent. How would the sample size change?