Utilizing Rasch measurement models to develop a computer adaptive self-report of walking, climbing, and running

Abstract

Purpose. The purpose of this paper is to show how the Rasch model can be used to develop a computer adaptive self-report of walking, climbing, and running.

Method. Our instrument development work on the walking/climbing/running construct of the ICF Activity Measure was used to show how to develop a computer adaptive test (CAT). Fit of the items to the Rasch model and validation of the item difficulty hierarchy was accomplished using Winsteps software. Standard error was used as a stopping rule for the CAT. Finally, person abilities were connected to items difficulties using Rasch analysis ‘maps’.

Results. All but the walking one mile item fit the Rasch measurement model. A CAT was developed which selectively presented items based on the last calibrated person ability measure and was designed to stop when standard error decreased to a pre-set criterion. Finally, person ability measures were connected to the ability to perform specific walking/climbing/running activities using Rasch maps.

Conclusions. Rasch measurement models can be useful in developing CAT measures for rehabilitation and disability. In addition to CATs reducing respondent burden, the connection of person measures to item difficulties may be important for the clinical interpretation of measures.

Keywords:

• Questionnaire development
• Item Response Theory
• Computer Adaptive Test

Notes

1. While technically, Rasch and the one-parameter IRT model are synonymous, Andrich [29] argues that the measurement philosophy underlying Rasch and IRT not reconcilable. For the purposes of this paper, we will use the term Rasch model and one-parameter IRT model interchangeably.

2. While the ICF Activity Measure consists of six constructs (gross upper extremity, fine hand, positioning/transfers; walking/climbing/running, wheelchair/scooter, and self-care) and 264 items, for purposes of this paper, we will focus only on the walking/climbing/running construct.