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Why do residuals and fitted plots look misleading?
Both the Residuals vs Fitted and the Scale-Location plots look like there are problems with the model, but we know there aren’t any. These plots, intended for linear models, are simply often misleading when used with a logistic regression model.
The first plot seems to indicate that the residuals and the fitted values are uncorrelated, as they should be in a homoscedastic linear model with normally distributed errors. Therefore, the second and third plots, which seem to indicate dependency between the residuals and the fitted values, suggest a different model.
Is there a plot.glm method in R?
R does not have a distinct plot.glm () method. When you fit a model with glm () and run plot (), it calls ?plot.lm, which is appropriate for linear models (i.e., with a normally distributed error term).
What are residuals in a linear regression plot?
That’s not the whole picture though. Residuals could show how poorly a model represents data. Residuals are leftover of the outcome variable after fitting a model (predictors) to data and they could reveal unexplained patterns in the data by the fitted model.
Which is better fitted or residuals in linear regression?
In this post we describe the fitted vs residuals plot, which allows us to detect several types of violations in the linear regression assumptions. You may also be interested in qq plots, scale location plots, or the residuals vs leverage plot.
What do the residuals in a logistic regression mean?
The deviance statistic (sum of squared unit-deviances) has an approximate chi-square distribution (when the saddlepoint approximation applies and under “Small dispersion asymptotics” conditions). Under these same conditions, the deviance residuals have an approximate normal distribution.