The research team from Problem 3 finds that the mean emphasis on appearance for books with girl protagonists is 30 (standard deviation = 8); for books with boy protagonists, it is 20 (standard deviation = 2).

a. Estimate the standard error of the mean difference. Calculate sample t.

b. Use the decision t from Problem 3, Part

d, to decide whether to reject the null hypothesis and draw a conclusion.

c. Are you surprised by the conclusion indicated by the test result? Explain why or why not.

d. Now the team wants to know whether themes in girl protagonist books have focused more or less on appearance since the new millennium. They divide the books with girl protagonists into two categories of time: published before 2000 and published in 2000 or later. What is the independent variable now? The dependent variable?