Exploratory examination of the scale structure of the Moorong Self-Efficacy Scale: Application of Rasch Measurement Theory.

OBJECTIVE

Exploratory application of the Rasch Measurement (RM) Model for evidence for reproducibility, conceptual/content validity, and structural validity of the Moorong Self-Efficacy Scale (MSES).

STUDY DESIGN

Secondary RM analysis of data collected in a randomized controlled trial comparing two exercise interventions for persons living with spinal cord injury (SCI).

SETTING

Community-dwelling persons living with SCI enrolled in an exercise study.

PARTICIPANTS

Adults ( = 79) enrolled in the parent study had a traumatic SCI > 3 months prior, injury level C5 to T12.

INTERVENTIONS

Not applicable.

OUTCOME MEASURE

The original MSES is a 16-item measure of self-efficacy with a 7-level response scale for un/certainty which was developed for use with persons living with SCI.

RESULTS

We addressed item misfit, infrequent category endorsement, and category step disorder by removing two items and reorganizing the rating scale. Rating scale changes removed category 4 (Neutral), combined categories 1-3 (Very Uncertain, Somewhat Uncertain, and Uncertain) for all items, and further combined certainty categories for two items. Principal components analysis of the residuals indicated a possible second dimension with a first-contrast Eigenvalue of 2.4. However, the contrasted item groups had explained variance <10% and a dis-attenuated correlation = 0.92 indicating they measure the same underlying trait. The small sample size precluded examination of differential item functioning.

CONCLUSIONS

Exploratory RM analysis of MSES produced a 14-item Rasch version which identified structural and content validity evidence concerns inherent in the original MSES. However, results could be biased by a small sample size and further study should examine the item content and rating scale structure with larger, more diverse samples of persons living with SCI.