extended · article · 2002

Evaluation of the Diabetes Self Care Scale: An Illustration of the Rasch Model of Measurement

Nantawadee P. Lee; William P. Fisher,; William P. Fisher Jr.

This pilot study illustrates the use of a Rasch measurement model to evaluate the psychometric properties of the Diabetes Self Care Scale (DSCS). A convenience sample of 50 adults with diabetes at two local hospitals (one for profit and one public) in southern Louisiana responded to the survey questions. The instrument is comprised of 27 items and 6 rating categories. The Bigsteps Rasch measurement software was used for all analyses. Results indicated that respondent separation reliability was low (0.63), but item separation reliability was satisfactory (0.91). Internal validity was supported. Twenty-six items measure a single construct of diabetes self care. Construct validity was supported by the meaningfulness of the item difficulty order and by the consistency of that order across respondents. Rating scale analysis revealed that middle categories were not distinct steps in the progre...