Although there's no commonly accepted agreement on how to assess the fit of a logistic regression, there are some approaches. The goodness of fit of the logistic regression model can be expressed by some variants of pseudo R squared statistics, most of which being based on the deviance of the model.
PseudoR2(x, which = NULL)
character, one out of
Cox and Snell's \(R^2\) is based on the log likelihood for the model compared to the log likelihood for a baseline model. However, with categorical outcomes, it has a theoretical maximum value of less than 1, even for a "perfect" model.
Nagelkerke's \(R^2\) (also sometimes called Cragg-Uhler) is an adjusted version of the Cox and Snell's \(R^2\) that adjusts the scale of the statistic to cover the full range from 0 to 1.
McFadden's \(R^2\) is another version, based on the log-likelihood kernels for the intercept-only model and the full estimated model.
Veall and Zimmermann concluded that from a set of six widely used measures the measure suggested by McKelvey and Zavoina had the closest correspondance to ordinary least square R2. The Aldrich-Nelson pseudo-R2 with the Veall-Zimmermann correction is the best approximation of the McKelvey-Zavoina pseudo-R2. Efron, Aldrich-Nelson, McFadden and Nagelkerke approaches severely underestimate the "true R2".
the value of the specific statistic.
G2 will only be reported with option
McFadden adjusted pseudo-\(R^2\)
Cox and Snell pseudo-\(R^2\) (also known as ML pseudo-\(R^2\))
Nagelkerke pseudo\(R^2\) (also known as CraggUhler \(R^2\))
McKelvey and Zavoina pseudo-\(R^2\)
Akaike's information criterion
log-Likelihood for the fitted model (by maximum likelihood)
log-Likelihood for the null model. The null model will include the offset, and an intercept if there is one in the model.
differenz of the null deviance - model deviance
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Veall, M.R., & Zimmermann, K.F. (1992) Evalutating Pseudo-R2's fpr binary probit models. Quality&Quantity, 28, pp. 151-164
Andri Signorell <firstname.lastname@example.org> with contributions of Ben Mainwaring <email@example.com> and Daniel Wollschlaeger