Transforming Variables

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Comparing Analyses

Transforming Variables

You can compare analyses by transforming variables in any window.

Create identical fit windows for DRILTIME = DEPTH.

Either delete METHOD from the first window or choose Edit:Windows:Copy Window in the second window.

Select DRILTIME in one of the fit windows.

Figure 21.18: Two Fit Windows, DRILTIME Selected

Choose Edit:Variables:log( Y ).

[menu]
Figure 21.19: Edit:Variables Menu

This recalculates the fit window using the log of the response variable (L_DRILTI). Now you have two fit windows for two different models.

Figure 21.20: Comparing Two Fit Analyses

In this case, the log transform did not improve the fit. To undo the log transform, you can choose Edit:Windows:Renew. In this chapter you have seen how to compare analysis windows that use different observations by extracting and excluding. You have also compared analyses using different variables by deleting and transforming. In the next chapter, you will see how to compare analyses using Group variables.

Related
Reading Transformations, Chapter 20.

Related
Reading Linear Models, Chapter 39.

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