ANALYSIS OF LIKERT SCALE DATA IN DISABILITY AND MEDICAL REHABILITATION RESEARCH

Many clinical evaluations are subjective, resulting in ordinal level m easurements. A widely used example in medical rehabilitation is the Fu nctional Independence Measure (FIM), which provides a measure of disab ility. The FIM is an 18-item, 7-point Likert scale ranging from comple te dependence to complete independence. Parametric statistics are comm only used for the analysis of ordinal data. However, Likert scales oft en lead to violation of many underlying assumptions. This study examin ed the comparative power of the t test with the Wilcoxon rank-sum test using real pretest/posttest data sets measured on an ordinal scale. F IM scores were obtained on 714 geriatric patients at admit and dischar ge from a rehabilitation hospital. A Fortran 77 program was written to sample with replacement from each admit and discharge data distributi on. Results indicated the Wilcoxon rank-sum test outperformed the t te st for almost every sample size and alpha level examined.