The mean of the residuals in logistic regression is always zero

Last year I wrote a post about how in linear regression the mean (and sum) of the residuals always equals zero, and so checking that the overall mean of the residuals is zero tells you nothing about the goodness of fit of the model. Someone asked me recently whether the same is true of logistic regression. The answer is yes for a particular residual definition, as I’ll show in this post.

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