title: Critique of the use of covariance adjustments for CA and MA in comparative studies of retarded and nonretarded persons.
abstract: Arguments were presented to show that the procedures of covariance adjustments for MA or for MA and CA are unsuited to the analysis of comparative data for retarded and nonretarded persons. Whatever the task and the performance levels of such subjects, the performance measures for both groups must always define a single continuous regression surface. It was proposed that graphical inspection of the regression surface will properly suggest the relative contributions of CA, MA, and IQ to the performance under study. Some of the data of the Temple longitudinal studies were used to illustrate the graphic procedure.
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D001076:Aptitude; D006801:Humans; D008607:Intellectual Disability / Q000150:complications*; D007360:Intelligence; D012044:Regression Analysis; D012107:Research Design