A Comparison of Two Measures of Physical Activity Among Adults with Physical Disabilities: The Issue of Scale Correspondence

The purpose of the study was to examine the issue of scale correspondence by testing the theory of planned behavior (TPB) using two models. Participants were 223 adults (M age = 45.4 years, SD = 10.8) with self-reported physical disabilities who completed an on-line survey. Using a cross-sectional design, participants completed demographic questions, TPB items, and two measures of physical activity. Path analyses, using one model that included a measure of behavior developed according to the TPB recommendations and a second model that used the Physical Activity Scale for Individuals with Physical Disabilities (PASIPD) generally supported the hypotheses of the TPB. Further, the model with the TPB scale (R (2) = .66) accounted for more variance in physical activity than the model using the PASIPD (R (2) = .15). Our findings are consistent with previous research; however, we argue that scale correspondence may not be statistically or philosophically appropriate.