According to a study, it takes an average of 330 minutes for taxpayers to prepare, copy, and mail an income tax return. A consumer watchdog agency selects a random sample of 40 taxpayers and finds the standard deviation of the time to prepare, copy and mail their tax return is 80 minutes.
a. What is the standard error of the mean in this example?
b. What is the likelihood the sample mean is greater than 320 minutes?
c. What is the likelihood the sample mean is between 320 and 350 minutes?
d. What is the likelihood the sample mean is greater than 350 minutes?
e. What assumption or assumptions do you need to make about the shape of the population?