Section Problems #12
Note that there are three problems.
Round all of your final answers to four decimal
places if necessary.
#1) Suppose that a researcher, using data on class size (
CS
) and average test scores (
TS
)
from 102 thirdgrade classes, estimates the OLS regression:
S
T
ˆ
= 500 – 5×(
CS
)
R
2
= 0.8, SER = 8
a) A classroom has 22 students.
What is the regression’s prediction for that classroom’s
average test score?
b) Last year a classroom had 19 students, and this year it has 23 students.
What is the
regression’s prediction for the change in the classroom average test score?
c) The sample average class size across the 102 classrooms is 21.4.
What is the sample
average of the test scores across the 102 classrooms?
d) What is the sample standard deviation of test scores across the 102 classrooms?
(Hint:
Review the formulas for R
2
and SER.)
#2) Suppose that a random sample of 200 twentyyear old men is selected from a
population and that these men’s height and weight are recorded.
A regression of weight
on height yields:
eight
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 Spring '08
 ABDUS,S.
 Regression Analysis, Standard Deviation, Variance, Kilogram, average test score

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