APA Dictionary of Psychology

(symbol: adj. R²; R²_adj) the square of the correlation between scores on a response or dependent variable and the values predicted by a set of independent variables after accounting for the number of predictors and the number of observations involved in the calculation. It gives the proportion of the variance in a response that is accounted for by its relationship with the predictors and yields a better estimate of the population variance than the adjusted R upon which it is based. Also called shrunken R2. See also coefficient of multiple determination.