An Item Response Theory Analysis of the Spiritual Assessment Inventory

Item response theory (IRT) was applied to evaluate the psychometric properties of the Spiritual Assessment Inventory (SAI; Hall & Edwards, 1996, 2002). The SAI is a 49-item self-report questionnaire designed to assess five aspects of spirituality: Awareness of God, Disappointment (with God), Grandiosity (excessive self-importance), Realistic Acceptance (of God), and Instability (in one's relationship to God). IRT analysis revealed that for several scales: (a) two or three items per scale carry the psychometric workload and (b) measurement precision is peaked for all five scales, such that one end of the scale, and not the other, is measured precisely. We considered how sample homogeneity and the possible quasi-continuous nature of the SAI constructs may have affected our results and, in light of this, made suggestions for SAI revisions, as well as for measuring spirituality, in general.