The use and interpretation of the Friedman test in the analysis of ordinal‐scale data in repeated measures designs
- 1 November 1996
- journal article
- review article
- Published by Wiley in Physiotherapy Research International
- Vol. 1 (4), 221-228
- https://doi.org/10.1002/pri.66
Abstract
The purpose of this paper is to review the use and interpretation of the Friedman two‐way analysis of variance by ranks test for ordinal‐level data in repeated measurement designs. Physical therapists frequently make three or more repeated measurements of the same individual to compare different treatments, or to assess the effect of a single treatment over time. When the measurements are ordinal‐scaled, such as some ratings of functional status and muscle strength, statistical significance may be determined by the Friedman test. We illustrate the use of the Friedman test and a post hoc multiple comparison test with data from 27 subjects whose performance on a lifting task was rated on three occasions by use of an ordinal scale. We discuss the interpretation of ordinal‐level data and recommend that therapists understand the limitations a measurement scale imposes on the inferences that can be made from these tests. Copyright © 1996 Whurr Publishers Ltd.Keywords
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