Introducing equating methodologies to compare test scores from two different self-regulation scales.

Standardizing the measurement tools that researchers use to assess the effectiveness of interventions would strengthen our ability to compare results across studies. In practice, however, standardization is difficult to implement, in part, because researchers prefer to use measurement tools that focus specifically on the components of their interventions. This paper demonstrates the usefulness of item response modeling linking methodology in comparing groups of participants who were administered different scales intended to measure the same underlying constructs. The Treatment Self-Regulation Questionnaire (TSRQ) as it relates to diet improvement provided the empirical application to demonstrate how two different scales that measure the same construct can be compared. The results showed that two eight-item TSRQ scales can be linked if they have at least four items in common. As expected, varying the number of linking items did not affect the reliability of the results; however, it significantly affected the relative rating with respect to the 15-item scale. In health behavior and health education research, linking methodologies can be used to compare results across studies that use slightly different versions of a scale to measure the same construct.