Chapter 7.2, Problem 21PB

Shared family phone plan A recent personalized information sheet from your wireless phone carrier claims that the mean duration of all your phone calls was µ = 2.8 minutes with a standard deviation of σ = 2.1 minutes.

1. a. Is the population distribution of the duration of your phone calls likely to be bell shaped, right-, or left-skewed?
2. b. You are on a shared wireless plan with your parents, who are statisticians. They look at some of your recent monthly statements that list each call and its duration and randomly sample 45 calls from the thousands listed there. They construct a histogram of the duration to look at the data distribution. Is this distribution likely to be bell shaped, right-, or left-skewed?
3. c. From the sample of n = 45 calls, your parents compute the mean duration. Is the sampling distribution of the sample mean likely to be bell shaped, right-, or left-skewed, or is it impossible to tell? Explain.