A comparison of Likert and visual analogue scales for measuring change in function
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Many controlled trials rely on subjective measures of symptoms or quality of life as primary outcomes. The relative merits of different response options for these measures is an important, but largely unexplored, issue. Therefore, we compared the responsiveness of seven-point Likert vs visual analogue scales (VAS) in a questionnaire measuring quality of life in chronic lung disease. The VAS and seven-point scale versions of the questionnaire were administered to 28 patients before and after completing an inpatient respiratory rehabilitation program of known benefit. For all four dimensions of the questionnaire (dyspnea, fatigue, emotional function, and mastery) the VAS showed a larger improvement than the seven-point scale when both were standardized on a scale of 0-10. However, in each case the variability of the improvement was greater using the VAS. The difference in improvement between the two scales was not statistically significant. We conclude that the two methods of presenting response options show comparable responsiveness. The ease of administration and interpretation of the seven-point scale recommend its use in clinical trials.
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