李克式量尺與視覺化類比量尺在生活品質量測上的比較：信度、效度與測量恆等性

Abstract

李克式量尺 (Likert-Type Scale) 和 視覺化類比量尺 (Visual Analogue Scale, VAS) 是量測生活品質 (Quality of Life, QOL) 最常用的兩種量尺。從過去學者對此兩種量尺的探討發現，這兩種量尺不論在設計上或是計分方式上都有很大的差異，而在具有這樣特性差異的前題下，此兩種量尺於量測生活品質上是否具有相同的心理計量特質就是個值得關注的議題。因此，本研究的目的是探討李克式量尺與視覺化類比量尺於生活品質量測上的比較。同時從三個方面進行探討：信度、效度與測量恆等性。 研究結果顯示，雖然視覺化類比量尺的信度表現較佳，但此兩種量尺的信度值都與過去研究所得的數值相仿，表示此兩種量尺在量測生活品質上都有適切的信度表現。同意度指標也顯示兩類量尺在生活品質量測上具有適切的一致性。然而，測量恆等性的分析顯示此兩種量尺所定義出的因素架構並不相同；更進一步的分析也顯示視覺化類比量尺較能有效的反映出生活品質的因素架構，具有較佳的建構效度。由於本研究中樣本多為健康與高教育的樣本，因此本文建議針對健康與高教育的樣本，可使用視覺化類比量尺做為生活品質的量測工具；然而對於其他特殊的群體 (例如：老人)，此兩種量尺的比較尚仰賴後續的研究與探討。

Likert-Type Scale and Visual Analogue Scale (VAS) are two common psychometrical 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 this present study, the author has 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. 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 to examine the validity and ME/I across Likert-type Scale and VAS. The result indicated that both Liker-Type Scale and VAS are easy for subjects to answer, and possessed adequate reliability, although reliability for VAS measures are consistently higher than for Likert-Type measures. The agreements between these two scales were high, indicating adequate reproducibility of test scores across the 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. In a word, VAS seemed to have better psychometric properties for measuring QOL over Likert-Type Scale. But according to the characteristics of subjects in the current study, the result will be applied to healthy and well-educated subjects, and the generalization on special populations (i.e., elderly and patients) is remained to be further explored.