This preview shows pages 1–2. Sign up to view the full content.
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
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
 Winter '09
 Rogosa,D
 Covariance, Variance

Click to edit the document details