The file MobileCommerce contains mobile commerce penetration values, the percentage of the country population that bought something online via a mobile phone in the past month, for twenty-eight of the world's economies:

a. Construct a 95% confidence interval estimate for the population mean mobile commerce penetration.
b. What assumption do you need to make about the population to construct the interval in (a)?
c. Given the data presented, do you think the assumption needed in (a) is valid? Explain.

17 15 15 13 27 12 20 23 99 16 6 19 14 148 15 23 11 37 17 19 27 18 18 15