For the population of individuals who own an iPhone, suppose p = 0.25 is the proportion that has 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 people who have an iPhone:
a. State the population distribution (that is, the probability distribution of X for each observation).
b. Find the mean of the sampling distribution of the sample proportion who have the app among the 50 people.
c. Find the standard deviation of the sampling distribution of the sample proportion who have the app among the 50 people.
d. Explain what the standard deviation in part c describes.