7.4 iPhone apps Let p = 0.25 be the proportion of iPhone owners who have a given app. For a particular iPhone owner, let x = 1 if they have the app and x = 0 otherwise.

For a random sample of 50 owners:

a. State the population distribution (that is, the probability distribution of X for each observation).

b. State the data distribution if 30 of the 50 owners sampled have the app. (That is, give the sample proportions of observed 0s and 1s in the sample.)

c. Find the mean of the sampling distribution of the sample proportion who have the app among the 50 people.

d. Find the standard deviation of the sampling distribution of the sample proportion who have the app among the 50 people.

e. Explain what the standard deviation in part d describes.