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Table 2 Overview of the analytic process using a Rasch model approach

From: Rasch analysis of the sense of coherence scale in a sample of people with morbid obesity – a cross-sectional study

Steps Psychometric property Measuring Statistical approach
1 Rating scale functioning Does the rating scale function consistently across items?  
2 Internal scale validity How well do the actual item responses match the expected responses from the Rasch model? Item goodness-of-fit statistics
3 Internal scale validity Is the scale unidimensional? Principal component analysis
4 Person-response validity How well do the actual individual responses match the expected responses from the Rasch model? Person goodness-of-fit statistics
5 Person-separation reliability Can the scale distinguish at least two distinct levels of sense of coherence in the sample tested? Person-separation index
6 Internal consistency Are item responses consistent with each other? Cronbach’s alpha coefficient
7 Differential item functioning (DIF) Are item difficulty calibrations stable in relation to demographic and clinical variables? Mantel-Haenszel statistics