Gillette Functional Assessment Questionnaire 22-item skill set: Factor and Rasch analyses

Aim To determine dimensionality and item-level properties of the Gillette Functional Assessment Questionnaire (FAQ) 22-item skill set using factor and Rasch analyses. Method A retrospective review of parent-reported FAQ 22-item skill set data was conducted of 485 individuals (273 males, 212 females; mean age 9y 10mo, SD 3y 10mo), including 289 with cerebral palsy and 196 with a variety of other neuromusculoskeletal conditions with orthopedic impairments. Factor analyses to validate unidimensionality of the skill set and Rasch analyses to determine relative item difficulty, item and test level information, and content coverage of the item set were performed. Differential item functioning analysis of sub-groups based on sex, diagnosis grouping, and age was conducted. Precision of score estimates for the item set was analyzed. Results The FAQ 22-item skill set demonstrates unidimensional structure and good item fit statistics. No floor or ceiling effects were noted. Differential item functioning (DIF) based on age was noted for seven items, four items showed diagnosis group-related DIF, and one item sex-related DIF. Precision was adequate in the mid-range range of abilities. Interpretation Based on this analysis, the FAQ 22-item skill set is a hierarchical set of interval scaled items suitable for measuring locomotor skill ability in children.