Answer Happy

7.4 iPhone apps The iPhone maker Apple announces that 25% of iPhone owners use a certain app. Let X be a bi- nary random variable that equals 1 if a randomly selected iPhone owner uses this particular app. and 0 otherwise. a. State the population distribution of X using the infor- mation Apple provides. (That is, give the proportion of times that you expect a randomly selected owner to use or not use the app.) b. For a random sample of 50 iPhone owners, 30 use the app. State the data distribution for X based on this sample.

c. Find the mean of the sampling distribution of the sam- ple proportion who use the app in a random sample of 50 owners. d. Find the standard deviation of the sampling distribu- tion of the sample proportion who use the app in a random sample of 50 owners. e. Explain what the standard deviation in part d describes.