Item response theory analysis of the spiritual well-being questionnaire

Recently, Gomez and Fisher (2003) published the Spiritual Well-Being Questionnaire (SWBQ). This is a self-rating measure with separate 5-item scales for personal, communal, environmental, and transcendental spiritual well-being. This study used item response theory (IRT) to examine the psychometric properties of these scales. A sample comprising 4462 participants from mainly secondary schools and universities completed the SWBQ. Samejima’s graded response model was used for the analyses. The results showed that the discrimination parameters for all items in the four scales were moderate to large. The threshold parameters showed adequate representation of the relevant traits from low to the mean trait level for personal, communal and environmental items, and from low to moderately high trait level for the transcendental items. With the exception of five items, all other items showed good item information function values, and therefore acceptable reliability. The findings also indicated that the number of response options could be decreased and increased at the low and high trait levels, respectively. Thus while there was general support for the psychometric properties of the SWBQ from an IRT perspective, there were also indications that this measure can be further improved.