10.18. Table 10.7 lists the mean salary, in thousands of dollars, of faculty on nine-month contracts in U.S.

institutions of higher education in 2003-2004, by gender and academic rank.

(a) Suppose that gender is the explanatory variable. Identify the response variable and the control variable.

(b) Describe the bivariate relationship between gender and salary.

(c) Describe the relationship between gender and salary, controlling for academic rank.

(d) A hypothesis of interest for these variables is

"Controlling for academic rank, annual salary and gender are independent." Draw a causal diagram thatis consistent with this hypothesis.

Refer to your interpretation in part (c), and comment on whether the hypothesis seems plausible.

(e) The overall difference of 12.1 thousand dollars between mean income of men and women is larger than the difference for each academic rank. Explain how this could be.

TABLE 10.8 Math Verbal Gender >' = 1 y = 2 y = 1 y = 2 Females 100 50 50 100 Males 50 100 100 50