Examination of the Problem Gambling Severity Index for Use with Older Adults: A Rasch Model Approach.

Research and prevalence studies commonly use the nine-item Problem Gambling Severity Index (PGSI; Ferris and Wynne in The Canadian Problem Gambling Index, 2001) to measure problem gambling severity in older adults. However, the appropriateness of the PGSI for use with older adults must be evaluated to ensure accurate interpretation of scores. This study evaluated the PGSI with older adults that gamble using a Rasch model approach, which has not yet been examined in the literature. Data from the Quinte Longitudinal Study (Wiiliams et al. in The Quinte Longitudinal Study of Gambling and Problem Gambling 2006-2011, Bay of Quinte region, Ontario [Canada] (V28), 2014) were utilized, accessed through the Gambling Research Exchange of Ontario (GREO). Using WINSTEPS.V5, a Rasch rating scale model was applied to an older adult sample from Ontario, Canada (n = 571, Mage = 66, range = 60-80 +) to assess: (1) the dimensionality and fit between individual PGSI items and the underlying latent construct of problem gambling; (2) utility of items and response options; and (3) potential differential item functioning (DIF) between genders. Using a larger sample (N = 3206, Mage = 45, range = 18-80 +), DIF was examined across three age subgroups. Results supported unidimensionality of the PGSI and item polarity (rpm range = 0.42-0.85). Infit and outfit statistics showed mixed model misfit for three items. The use of three response options were deemed productive for measurement, but almost always was not frequently endorsed. Model-person separation (1.00) and reliability (0.50) were poor, and model-item separation (6.12) and reliability (0.97) were excellent. There was no significant DIF between older adults by gender. Three items showed significant DIF between older and younger adults. Possible modifications to improve the PGSI for use with older adults are discussed.