DO LIKERT-TYPE SCALE AND VISUAL ANLOGUE SCALE MEASURE THE SAME QUALITY OF LIFE?

Author(s)

Grace Yao, PhD, Professor1, Yu-Yu Hsiao, Master, Graduate Student21National Taiwan University, Taipei, Taiwan; 2 National Taiwan University, Taipei, Taiwan, Taiwan

OBJECTIVES: Likert-Type Scale and Visual Analogue Scale (VAS) are two common psychometric methodologies for measuring Quality of Life (QOL). However, these two scales are different from their constructions and rating methods. Besides, whether these different attributes will result in different psychometric properties for Likert-Type Scale and VAS on measuring QOL has not yet been examined. Thus in the present study, we compared Likert-Type Scale and VAS for measuring QOL in three aspects: 1) the degree of agreement between these two scales; 2) the evaluation of the Measurement Equivalence/Invariance (ME/I) over these two scales for the assessment of QOL; and 3) the investigation of construct validity of theoretical framework of QOL across these two scales. METHODS: A total of 496 adult subjects were used in the current study (58.9% female, n= 292; 40.2% male, n=200; mean age=24.64 yrs). Each subject was asked to fill in the WHOQOL-BREF in two different visions, one was measured by Likert-type scale and the other was by VAS. Reliability analyses were applied by using Cronbach’s alpha coefficient and split-half coefficient. Besides, agreement analyses were applied by using Pearson’s r, Intraclass Correlation Coefficient (ICC), Lin’s Concordance Correlation Coefficient (CCC), and Bland-Altman Plot. Finally, a MTMM matrix and Confirmatory Factor Analysis (CFA) were used for examining the validity and ME/I across Likert-type Scale and VAS. RESULTS: The result indicated that both Liker-Type Scale and VAS were easy for subjects to answer, and possessed adequate reliability although reliability for VAS measures were consistently higher than Likert-Type measures. The agreements between these two scales were high, indicating adequate reproducibility of test scores across scales. In ME/I analyses, the result showed that VAS measures and Likert-Type measures did not reflect the same structure, furthermore, the VAS defined a better construct of QOL. CONCLUSIONS: VAS seemed to have better psychometric properties for measuring QOL over Likert-Type Scale. More discussion on the two measurement scales will be provided in our presentation.

Conference/Value in Health Info

2008-11, ISPOR Europe 2008, Athens, Greece

Value in Health, Vol. 11, No. 6 (November 2008)

Code

PMC27

Topic

Methodological & Statistical Research

Topic Subcategory

PRO & Related Methods

Disease

Multiple Diseases

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