st: RE: standardized parameter for dichotmious variable in a regr

[Steven Samuels <ssamuels@albany.edu>]

I agree with Maarten.

The beta coefficients measure  impact on the conditional MEAN of Y.   
If you believe that r-square measures  strength of
association in the simple X-Y case, then you should use the partial r  
square in multiple regression.

This works for dichotomous and continuous covariates.  The partial  
correlations are ranked in
the same order as the absolute value of the t-statistics for each  
covariate.

Think of a simple X-Y regression.  You can have a "strong" X-Y   
association (as indicated by the SAME  high R-square)
in two ways, holding the X's constant.

1. Large slope but relatively high residual SD.
2. Small slope but small residual SD.

In fact, holding the X's constant, one regression plot can be  
transformed into the other by changing the
units of Y.  Only r-square is invariant to this kind of  
transformation in the Y's (or in the X's, for that matter.)


Steve Samuels
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