Rasch analyses of the wheelchair use confidence scale

Abstract

Objectives: To compare the functioning of the 101-point response format of the Wheelchair Use Confidence Scale (WheelCon) with shortened 11-point formats, and to evaluate the scale's measurement properties using principal components and Rasch analyses.

Design: Secondary analysis of cross-sectional data.

Setting: Community.

Participants: Volunteer participants were manual wheelchair users (N=220) ≥19 years of age, with ≥6 months' experience with daily wheelchair use and no cognitive impairment.

Interventions: None.

Main outcome measure: 65-item WheelCon.

Results: The 11-point response format outperformed the original 101-point format. Principal component analyses confirmed the presence of 2 dimensions: mobility efficacy and self-management efficacy. Thirteen items in the mobility efficacy subscale and 8 items in the self-management efficacy subscale fit the Rasch Rating Scale model. Five items misfit the model developed using the 21 items from both subscales. In each of the 13- and 8-item subscales, and the 21-item short form, the 2 lowest and highest scores had internal consistency reliability estimates <.70; all other scores had reliability estimates >.70.

Conclusions: The WheelCon is composed of 2 dimensions. The recoded measurements using a 0-to-10 response scale from the 13-item mobility and 8-item self-management efficacy subscales have good reliability, as do the measurements from the 21-item WheelCon Short Form. The use of the subscales, the short form, or both, depends on the context in which they are being considered. Research to establish the reliability and validity of the measurements using the 0-to-10 response format is warranted.

Keywords: Factor analysis; Outcome assessment (health care); Psychometrics; Rehabilitation; Self efficacy; Wheelchairs.

Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Figures

Figure 1

Scree plot showing two dominant dimensions

Figure 2

Reliability and SEM of the Mobility efficacy, Self-management efficacy, and WheelCon Short Form scores

Figure 2

Reliability and SEM of the Mobility efficacy, Self-management efficacy, and WheelCon Short Form scores