Presents the bivariate normal probability distribution as a method for estimating the prevalence of giftedness. The bivariate model requires the specification of two cutoff values for two selection variables and information regarding the size of the correlations between variables. The use and interpretation of bivariate estimates is discussed.…

This book discusses constructing variables and making measures. It begins by outlining the qualities a number must meet before it qualifies as a measure of something. The basis is the measurement philosophy of G. Rasch. The first requirement for making good measures is good raw material. To achieve the possibility of comparisons, the data must…