Statistics 101
  Data Analysis and Statistical Inference
 

Instructions for lab 6

Lab Objective

The purpose of the lab is to address a policy question using methods that we have learned in class.

Lab Procedures

Does spending more money on education have an impact on students' learning?    Some evidence suggests a positive impact, whereas other evidence suggests hardly any impact at all.  In this lab, we'll look at a particular aspect of this question, namely the association between statewide expenditures on education and SAT scores.

Open the data set satjse.jmp by clicking on the link.   The file contains data from 1997 on all 50 states of the U.S. for the following variables:

State:                                  state name.
Expenditure:                      Per pupil expenditure in state in thousands of dollars.
Student/Faculty Ratio:      Number of faculty per pupil in state.
Salary:                               Average salary for teachers in state in thousands of dollars.
Percent taking:                  Percentage of students taking the SAT, expressed as % times 100.
Verbal:                               Average score on verbal part of SAT for students who took it.
Math:                                 Average score on math part of SAT for students who took it.
Total SAT Score:               Average combined score of SAT for students who took it.
Expenditure (100s):           Per pupil expenditure in state in hundreds of dollars.

These data were collected by Professor Lynn Guber of the University of Vermont.

Questions:

1)  Describe the general trend in the relationship between expenditures and total SAT scores.

2)  Describe the general trend in the relationship between percent taking and total SAT scores.

3)  Describe the general trend in the relationship between percent taking and expenditures.

4)  Which variable is the best linear predictor of total SAT score (i.e. has the strongest linear relationship with total SAT score)?  Don't consider verbal or math SAT as predictors; they're components of the total score, so of course they're not what we're interested in.

5)  The political commentator George Will examined a similar scatter plot between expenditures per pupil and average combined SAT score.  He concluded that, at the state-level, spending more money per pupil does not cause average SAT scores to increase (The Washington Post, September 12, 1993). 

Explain why Will should not make this causal claim based on the scatter plot.  Explain how variables other than expenditures could explain the pattern in the scatter plot.  Use the information in the data to make your arguments.  Failing to cite evidence from the data will lose credit.