Generalized Linear Models – Diagnostic Techniques for General Linear Models

deviancediagnosticgeneralized linear modelresiduals

Pearson residuals follow normal distribution. We plot them against predicted values to see if the model is good.

Why would we plot deviance residuals against predicted values? Deviance residuals don't follow normal distribution, right? What's the point of plotting them?

Best Answer

Pearson residuals in general do not follow a normal distribution.

Deviance residuals don't follow normal distribution, right?

They don't, but they will typically be much closer to being normally distributed than Pearson residuals.

Here's an example with a Poisson model applied to actually Poisson data

normal QQ plots of various GLM residuals

Clearly the working residuals are the least normal-looking. The Pearson residuals are better but still show a clear curvature. The straightest Q-Q plots are for the deviance and Anscombe residuals. This is fairly typical across a number of GLM models.

None of them are actually normal, but the Pearson residuals are clearly skewed, while the deviance residuals are much more nearly symmetric.

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