Generalized Linear Model (GLM) Unique Features - Efficient Computations for Balanced ANOVA Designs
Most between ANOVA designs can be analyzed much more efficiently when they are balanced, i.e., when all cells in the ANOVA design have equal n, when there are no missing cells in the design, and, if nesting is present, when the nesting is balanced so that equal numbers of levels of the factors that are nested appear in the levels of the factor(s) that they are nested in. In that case, the X'X matrix (where X stands for the design matrix) is a diagonal matrix, and many of the computational necessary to compute the ANOVA results (such as matrix inversion) are greatly simplified.
STATISTICA GLM contains an option to "instruct" the program that the design is balanced, and that the more efficient computational methods can be used (option Huge balanced ANOVA on the Quick tab of the GLM Startup Panel, or the BALANCED option used in conjunction with keyword SSTYPE using GLM syntax). Even very large designs with effects with degrees of freedom in the hundreds can thus be analyzed in mere seconds, while the general computational procedures (that do not assume a balanced design) may take several minutes to accomplish the same.
Some Unique Features and Facilities of GLM