Using the Fit Special command, you can transform Y and X. Transformations include the following: log, square root, square, reciprocal, and exponential. You can also constrain the slope and intercept, fit a polynomial of specific degree, and center the polynomial.
|
To turn off polynomial centering, deselect the Centered Polynomial check box. See The Specify Transformation or Constraint Window. Note that for transformations of the X variable, polynomial centering is not performed. Centering polynomials stabilizes the regression coefficients and reduces multicollinearity.
|
|
Depending on your selections in the Fit Special window, you see different reports and menus. The flowchart in Example of Fit Special Flowchart shows you what reports and menus you see depending on your choices.
However, if you transformed Y, the Fit Measured on Original Scale report appears. This shows the measures of fit based on the original Y variables, and the fitted model transformed back to the original scale.