Background/Purpose The purposes of this study were to develop and calibrate the obesity risk measurement scale (ORMS) using the Rasch model, and to validate the scale through known group difference approach.
Method Based on the literature review and consultation of content and measurement experts, the 21-item ORMS was generated. The ORMS consists of physical activity, meal, heredity, and psychology constructs. The scale was administered to 398 university students. Rasch measurement computer program, FACETS(Linacre, 2002), was used to analyze the data. Model data fit was determined by Infit and Outfit statistics(≥0.70 and ≤1.30). One-way ANOVA was used to establish the known group difference validity evidence of the ORMS. Alpha level was set at 0.05.
Analysis/Results Nineteen of the 21 items had good model-data fit with acceptable fit statistics. The 2 items were eliminated from the final estimation. Overall, the 4 rating categories functioned well; threshold advanced with category. The item separation index (7.36) and separation reliability statistic (.98) provided evidence that the items had good variability with a high degree of confidence in replicating placement of the items from another sample. There was a statistically significant mean difference in person's logits score between categorized BMI group(<23, ≥23), F(1, 396) = 4.089, p < 0.05. This result supports the known group difference validity evidence of the ORMS.
Conclusions Results provided support for using the ORMS. The scale can be used to assess the risk of obesity of individuals and provide health information.
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