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Modeling and Multivariate Methods - SAS

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Chapter 4 Fitting Stepwise Regression Models 135<br />

Overview of Stepwise Regression<br />

Overview of Stepwise Regression<br />

In JMP, stepwise regression is a personality of the Fit Model platform. The Stepwise feature computes<br />

estimates that are the same as those of other least squares platforms, but it facilitates searching <strong>and</strong> selecting<br />

among many models.<br />

Example Using Stepwise Regression<br />

The Fitness.jmp (<strong>SAS</strong> Institute Inc. 1987) data table contains the results of an aerobic fitness study. Aerobic<br />

fitness can be evaluated using a special test that measures the oxygen uptake of a person running on a<br />

treadmill for a prescribed distance. However, it would be more economical to find a formula that uses<br />

simpler measurements that evaluate fitness <strong>and</strong> predict oxygen uptake. To identify such an equation,<br />

measurements of age, weight, run time, <strong>and</strong> pulse were taken for 31 participants who ran 1.5 miles.<br />

Note: For purposes of illustration, certain values of MaxPulse <strong>and</strong> RunPulse have been changed from data<br />

reported by Rawlings (1988, p.105).<br />

1. Open the Fitness.jmp sample data table.<br />

2. Select Analyze > Fit Model.<br />

3. Select Oxy <strong>and</strong> click Y.<br />

4. Select Weight, Runtime, RunPulse, RstPulse, MaxPulse, <strong>and</strong> click Add.<br />

5. For Personality, select Stepwise.

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