B – 134 Application of Cohen’s q to prorated MMPI-2 scales

Abstract Objective Transitioning between different versions of assessment scales necessitates proration to provide a way of utilizing old data for updated interpretations. However, uncertainty remains as few studies have examined the practical effect of proration within a strict scale to scale context (Van Der Heijden et al., 2010; Tarescavage et al., 2015). Cohen’s q is a useful practical effect metric for evaluating consistency between two versions of scales. It quantifies the difference between correlation coefficients, providing a way to assess how well prorated scales align with their originals. Method This study examines MMPI-2-RF scales through calculating Cohen’s q. Active-Duty service members (n = 587) were part of a full neuropsychological assessment battery for post-deployment job related deficits (Puente et al., 2020). MMPI-2 scales were prorated to MMPI-2-RF scales using standard methods (Tellegen & Ben-Porath, 1992; Van Der Heijden et al., 2010). Cohen’s q was calculated via Fisher’s Z transformation. Interpretative thresholds were based on conventional standards (Cohen, 1988). Results Most scales exhibited a less than small effect with their MMPI-2 counterparts, while several Cohen’s q values fell outside acceptable ranges (e.g. [Fp] q = 0.29, 95% CI [.22 - .34]), suggesting meaningful discrepancies. Certain prorated scales showed inconsistencies in original construct intention. Conclusion Findings highlight proration may hold discrepancies for certain scales of the MMPI-2-RF. Such inconsistencies raise concerns with interpretive accuracy of prorated data, particularly in clinical and high-stakes assessment settings where precision and interpretation are critical. Clinicians should be cautious when interpreting prorated scales, particularly when assessing constructs with notable deviations in Cohen’s q.