REGRESSION OPTIONS

You can produce various different plots by ticking the one you want under the plot tab of the Linear Regression dialog box. Display a plot of the response variable versus the fitted values by selecting Response vs Fit. You should get the plot below.

Below are two more examples of plots that can be generated. The first is a plot of the residuals versus the fitted values and the second is a residual-fit spread plot. The latter is a visual analog of the multiple R-squared statistic and it compares the spread of the fitted values to the spread of the fitted values.

Other points about regression are:

Regressing X on Y doesn't give the same line as regressing Y on X.
It is dangerous to extrapolate (use the fitted line to predict what happens outside the range of the data). e.g. intake when whc=0.
Genstat can also be used if the relationship is not linear, or there is more than one explanatory variable.

REGRESSION OPTIONS

Basic statistics in S-Plus 18.8.99 Page: 27 of 28.

Basic statistics in S-Plus 18.8.99
Page: 27 of 28.