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The main objective of this project was to investigate some aspects of the diagnostic and prognostic validity of the five-element rank order repertory grid (REP 5). This has been attempted at various levels of analysis with 48 nocturnal enuretic boys, aged 8 to 14, undergoing highly standardized hypnotherapy. REP 5, with neutral elements (photographs) and supplied constructs, was administered 5 times over an 8 month period, i.e. at the pretherapy; mid-therapy; end-therapy; 6 week and the 6 month follow-up stages. Each subject acted as his mm control and in addition a nontreatment control group awaiting similar therapy was used. On the basis of current theory and relevant adult research findings, certain hypotheses were formulated to assess the validity of REP 5. This provided a framework within which the task was to determine whether REP 5 could register (a) in a predictable and meaningful way the expected relationships between the relevant variables; and (b) changes in these relationships. The grid performances were also validated against an empirical criterion which was objectively measurable, i.e. nights dry. Results indicated that the REP 5 was reasonably effective in registering in a meaningful way the status and changes in variables during and after therapy. It appeared that the REP 5 has a significant diagnostic and prognostic utility value. Its efficacy as an instrument seems to be mainly limited by the ability of its designer to match the test design with the purposes for which it was intended.

The interpretation of data from psychological experiments often involves the analysis and comparison of curves, like the electrocardiogram, spectral sensitivity, or dose-response curves. Existing statistical techniques are often inadequate for making this type of analysis. This thesis presents alternative methods for handling the data comprising curves and discusses the advantages of these techniques against those of existing methods.

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abstract: Item response theory (IRT) and related latent variable models represent modern psychometric theory, the successor to classical test theory in psychological assessment. While IRT has become prevalent in the assessment of ability and achievement, it has not been widely embraced by clinical psychologists. This appears due, in part, to psychometrists' use of unidimensional models despite evidence that psychiatric disorders are inherently multidimensional. The construct validity of unidimensional and multidimensional latent variable models was compared to evaluate the utility of modern psychometric theory in clinical assessment. Archival data consisting of 688 outpatients' presenting concerns, psychiatric diagnoses, and item level responses to the Brief Symptom Inventory (BSI) were extracted from files at a university mental health clinic. Confirmatory factor analyses revealed that models with oblique factors and/or item cross-loadings better represented the internal structure of the BSI in comparison to a strictly unidimensional model. The models were generally equivalent in their ability to account for variance in criterion-related validity variables; however, bifactor models demonstrated superior validity in differentiating between mood and anxiety disorder diagnoses. Multidimensional IRT analyses showed that the orthogonal bifactor model partitioned distinct, clinically relevant sources of item variance. Similar results were also achieved through multivariate prediction with an oblique simple structure model. Receiver operating characteristic curves confirmed improved sensitivity and specificity through multidimensional models of psychopathology. Clinical researchers are encouraged to consider these and other comprehensive models of psychological distress. / Dissertation/Thesis / Ph.D. Psychology 2011