According to a report from a business intelligence company, smartphone owners are using an average of 18 apps per month. Assume that number of apps used per month by smartphone owners is normally distributed and that the standard deviation is 4.

a. If you select a random sample of 25 smartphone owners, what is the probability that the sample mean is between 17.5 and 18.5?

.468

(Round to three decimal places as needed.)

b. If you select a random sample of 25 smartphone owners, what is the probability that the sample mean is between 17 and

18?

.394

(Round to three decimal places as needed.)

c. If you select a random sample of 100 smartphone owners, what is the probability that the sample mean is between 17.5

and 18.5?

enter your response here

(Round to three decimal places as needed.)