extended · article · 2013

Rasch analysis of the General Self-Efficacy Scale in a sample of persons with morbid obesity

Tore Bonsaksen; Anders Kottorp; Caryl Gay; May Solveig Fagermoen; Anners Lerdal; Mark Wilson

BACKGROUND: Self-efficacy is needed for effectuating lifestyle changes, and it is therefore an important target related to health. The purpose of this study was to evaluate the psychometric properties of the General Self-Efficacy Scale (GSE) using Rasch analysis in a sample of adults with morbid obesity. METHODS: A convenience sample of adults with morbid obesity was recruited from patient education courses. A total of 141 participants completed the GSE and a demographic questionnaire at the beginning of the course. The statistical approach included analysis of rating scale function, item fit to the Rasch partial credit model, unidimensionality, aspects of person-response validity, person-separation reliability, and differential item function. A version omitting items with poor fit to the Rasch model was also evaluated. RESULTS: The rating scale did not advance monotonically for item #2 ...