hw5.ass - Page 1 of 3 Stat209/Ed260 D Rogosa Assignment 5....

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Stat209/Ed260 D Rogosa 2/8/09 Assignment 5. The many uses and forms of analysis of covariance --------------------------------------- 1.Background: categorical predictors A study of several hundred professors' salaries in a large American university in 1969 (AER, 1973, p.469) yielded the following prediction equation: S = 1900 + 230*B + 18*A + 100*E + 490*D + 190*Y + 50*T - 2400*X where S is annual salary, B is number of books written, A number of ordinary articles, E number of excellent articles, D number of Ph.D.'s supervised, Y years experience, T = 1 if student evaluations above median, 0 otherwise, X = 1 if female, 0 otherwise. For a prof with B=A=E=D=X=1 and Y=5, what's the expected change in salary if she goes from very good to poor student evaluations? Mean salaries were $16,100 for males and $11,200 for females. What is the value of the slope from a simple S on X regression? ---------------------------------------- 2. Background: standard analysis of covariance. A researcher is studying the effect of an incentive on the retention of subject matter and is also interested in the role of time devoted to study. Subjects are randomly assigned to two groups, one receiving (C3 = 1) and the other not receiving (C3 = 0) an incentive. Within these groups, subjects are randomly assigned to 5, 10, 15, or 20 minutes of study (C2) of a passage specifically prepared for the experiment. At the end of the study period, a test
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hw5.ass - Page 1 of 3 Stat209/Ed260 D Rogosa Assignment 5....

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