A measure for judging the extent to which a model explains the variation in a set of data when the parameter estimation is carried out using the method of maximum likelihood. The deviance, D, is given by

,
A summary of how well a model fits the data is provided by McFadden's R2 (which is also known as the likelihood ratio index) defined by

,
A Dictionary of Statistics. Second edition revised. Copyright © Oxford University Press, 2008. All rights reserved.