# [R] the observed "log odds" in logistic regression

From: Bin Yue <leffgh_at_163.com>
Date: Mon, 10 Dec 2007 19:42:36 -0800 (PST)

Dear list:

I've known the mathematical basis for logistic regression.However I am still not so sure about the "logit "

For a categorical independent variable, It is easy to understand the procedures how "log odds" are calculated. As I know, First the observations are grouped according to the IV and DV, generating a contingency table.The columns are the levels of IV, and the rows are the levels of DV(0, or 1).For each column,we get the proprotions for DV=0 and DV=1 at given IV. Using the proportions the log odds can be computed.Is that right?

And about the residuals. It seems that the residual is not the actual DV minus the fitted probability. For in my model extreme residuals lie well beyond (0,1). I wonder how the residual is computed.

Bin Yue

Best regards,
Bin Yue

student for a Master program in South Botanical Garden , CAS
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