Measuring change with multiple Visual Analogue Scales: Application to tense arousal

Although the visual analogue scale (VAS) may be useful for measuring change on subjective and potentially transient phenomena, there is concern about the reliability and construct validity of the associated measurement variables. The present study reports evidence for tau-equivalence of change scores as-sociated with VASs designed for assessing tense arousal with synonymous indicators. This psychometric property allows an estimation of the true-score structure of the cross-sectional measurement variables in a longitudinal SEM model, including method effects. Findings suggest that VASs asso-ciated with synonymous indicators may yield highly reliable measurement variables. However, imperfect dynamic bipolarity was observed when data based on antonymous indicators were introduced into the analyses, a rather puzzling effect, which deserves further elaboration. To monitor subjective and potentially transient phenomena like pain and mood in patients, sensitive and easily administered assessment techniques are required, especially when pa-tients are requested to rate themselves repeatedly. The well-known visual analogue scale (VAS), also called the graphic rating scale (Freyd, 1923), is appealing for this reason. "A VAS is a straight line, the end anchors of which are labeled as the extreme boundaries of the sensation, feeling, or response to be measured " (Wewers & Lowe, 1990, p. 227). The respondent is asked to mark the line to indicate the intensity of the internal stimulus, and a linear function of the corresponding distance is assumed to measure it (Hofmans & The