n.1. any behavior that differs significantly from what is considered appropriate or typical for a social group. Also called deviancy. 2. in statistics, a measure of the goodness of fit between a smaller hierarchical model and a fuller model that has all of the same parameters plus more. If the deviance reveals a significant difference, then the larger model is needed. If the deviance is not significant, then the smaller, more parsimonious model is retained as more appropriate.