Limitations of Neuropsychological tests and Remedial Measures
Keywords:Equivalent scores, Factorial validity, Neuropsychological Test Battery, Normal distribution, Theoretical reliability
Background: Neuropsychological tests differ in terms of length (number of items), width (number of response-categories/levels), sub-classes or dimensions covered, psychometric documentation for unambiguous interpretations, responsiveness, discriminating value, etc. and scores are not comparable.
Aim: To address methodological issues of neuropsychological testing and suggests remedial measures by transforming discrete item scores to continuous scores in ratio scale following normal distribution for meaningful evaluation of measurement properties and better utilization of such tests.
Methods: Using data driven weights to response-categories of different items, ordinal item scores are converted to equidistant score (E-scores) in ratio scale with fixed zero point. Proposed scores (P-scores) obtained from E-scores via standardization and linear transformation follows normal distribution, parameters of which can be obtained from data. Sub-class scores and test scores are obtained as sum of item-wise P-scores.
Results: Normally distributed P-scores facilitate aggregation with cardinal measures like number of errors, time taken, etc. and offer platform for parametric analysis including statistical testing. In addition, the proposed method helps to find reliability as per theoretical definition, factorial validity avoiding criterion variable, discriminating value, assessment of progress/deterioration of one or a group of patients, efficiency of classification, equivalent scores of two neuropsychological tests, etc.
Conclusion: Proposed scores following normal distribution and satisfying desired properties of measurement is recommended. Practicing psychiatrists and researchers can derive benefits of the proposed score for meaningful comparisons, classifications, equating premorbid scores, and assessment of progress or deterioration.