A reference scale method for constructing neuropsychological test batteries.

Scaling of neuropsychological test variables requires knowledge of test parameters. This is a study of the parameters for 12 tests in the Rennick Index of the Halstead-Reitan Battery, using 732 subjects. z-score distributions were plotted. Great variability among test distributions indicated that, for brain-damaged subjects: the range is much greater than for normals; maximum z scores ranged from 3.8 to 27.3 for different tests; the form of the distributions was highly variable, ranging from normal to highly skewed distributions. Thus, the same z scores indicated quite different amounts of impairment on different tests. This raises questions regarding the applicability of z and T scores to a brain-damaged population. The second part of this study demonstrated how scaled scores, indicating equal amounts of impairment, could be constructed. This method used a reference scale produced by averaging control subjects' z scores on 12 tests. Individual scaled scores were obtained through a linear regression prediction.