Example Using Stepwise Regression
In this example, you use the Stepwise personality of the Fit Model platform to select significant variables in a linear regression model modeling oxygen uptake. Aerobic fitness can be evaluated using a special test that measures the oxygen uptake of a person running on a treadmill for a prescribed distance. However, it would be more economical to find a formula that uses simpler measurements that evaluate fitness and predict oxygen uptake. To identify such an equation, measurements of age, weight, run time, and pulse were taken for 31 participants who ran 1.5 miles.
1. Select Help > Sample Data Folder and open Fitness.jmp.
2. Select Analyze > Fit Model.
3. Select Oxy and click Y.
4. Select Weight, Runtime, RunPulse, RstPulse, MaxPulse, and click Add.
5. For Personality, select Stepwise.
Figure 5.1 Completed Fit Model Launch Window
Validation is available only in JMP Pro.
6. Click Run.
Figure 5.2 Stepwise Report Window
To find a good oxygen uptake prediction equation, you need to compare many different regression models. Use the options in the Stepwise report window to search through models with combinations of effects and choose the model that you want.