10) A 2011 NBC news survey found that 80% of a sample of 4500 U.S. teens said they own an MP3 player. Assume that the sample is an SRS.
a) Based on this sample, calculate a 90% confidence interval for all U.S. teens who own an MP3 player.
b) Without calculating, suppose we compute a large-sample 80% Confidence Interval for all U.S. teens who own an MP3 player. Would the margin of error be larger or smaller than in (a)? Why?
c) How many U.S. teens must be interviewed to estimate the proportion who own an MP3 player within +/- 0.02 with a 99% Confidence using the large-sample confidence interval? Use 0.5 as the conservative guess for the value of p*.