Nonequivalent survey consolidation: an example from functional caregiving.

Functional Caregiving (FC) is a construct about mothers caring for children (both old and young) with intellectual disabilities, which is operationally defined by two nonequivalent survey forms, urban and suburban, respectively. The purposes of this research are, first, to generalize school-based achievement test principles to survey methods by equating two nonequivalent survey forms. A second purpose is to expand FC foundations by a) establishing linear measurement properties for new caregiving items, b) replicate a hierarchical item structure across an urban, school-based population, c) consolidate survey forms to establish a calibrated item bank, and d) collect more external construct validity data. Results supported invariant item parameters of a fixed item form (96 items) for two urban samples (N = 186). FC measures also showed expected construct relationships with age, mental depression, and health status. However, only five common items between urban and suburban forms were statistically stable because suburban mothers' age and child's age appear to interact with medical information and social activities.