Introduction to Econometrics 3rd Edition by James Stock, Mark Watson

Exercise 9

Suppose that a researcher, using data on class size ( CS ) and average test scores from 100 third-grade classes, estimates the OLS regression

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 100 classrooms is 21.4. What is the sample average of the test scores across the 100 classrooms
d. What is the sample standard deviation of test scores across the 100 classrooms