The FIFA World Cup was one of the biggest sporting events of 2018. The file WC2018Players contains data of the players of the 32 teams that qualified for the event. A dummy variable is included to indicate whether a player is also a captain.

For the ages of captains and non-captains separately:

a. Construct a 95% percent confidence interval estimate for the population mean age.

b. Interpret the intervals constructed in (a).

c. What conclusions can you reach about the ages of captains and non-captains?

d. What assumption must you make about the population distribution on order to construct the confidence interval estimate in (a)?

e. Do you think that the assumption needed in order to construct the confidence interval estimate in (a) is valid? Explain.