3. The data file Alertness.txt contains data from a study on the effect on alertness of two doses of a medication on male and female subjects. This is a 2 × 2 design with four replications. The question of interest is whether changing the dose changes the average alertness of male and female subjects by the same amount.

(a) Express in words the null hypothesis that should be tested for answering the question of interest (use statistical terminology).

(b) Use either R commands or hand calculations to test the hypothesis in part (a).