Expectancy of impaired neuropsychological test scores in a non-clinical sample

Two methods were addressed to evaluate the incidence of false positive impairment on tests in neuropsychological evaluation. One method used a mathematical model based on the binomial theory (Ingraham & Aiken, 1996) to offer predictions based on probability. The model sets boundaries to determine when score variations would occur by chance and is therefore useful for identifying when cases exceed established boundaries. In addition, the present study examined test performance in a non-clinical sample of 94 college students via the Halstead Reitan Neuropsychological Test Battery. Results found that 15% of the sample had impairments suggested by the Halstead Impairment Index, using criteria established by Reitan and Wolfson (1993). In addition, one-half of the sample obtained impaired scores on one or two tests. These results are consistent with what the binomial model predicted. The model would therefore serve as a useful resource for clinicians when considering the probability of impaired test performance.