It is generally thought that sales spike during the year-end holidays. So the sales during year-end holidays were omitted, and the new summary statistics was determined as given below.

Year N Mean StDev Minimum Maximum First half 194 17947 2047 10931 23454 Second half 248 21861 1083 19972 25396 Do sales appear to be higher during the second half of the year after omitting those data most inf luenced by year-end holidays?

a) Write the null and alternative hypotheses.

b) Test the null hypothesis, and state your conclusion.

c) Suggest additional factors that may inf luence fiction books’ sales not accounted for in this exercise.