Visual analogue scale
The visual analogue scale or visual analog scale (VAS) is a psychometric response scale which can be used in questionnaires. It is a measurement instrument for subjective characteristics or attitudes that cannot be directly measured. When responding to a VAS item, respondents specify their level of agreement to a statement by indicating a position along a continuous line between two end-points.
Comparison to other scales
This continuous (or "analogue") aspect of the scale differentiates it from discrete scales such as the Likert scale. There is evidence showing that visual analogue scales have superior metrical characteristics than discrete scales, thus a wider range of statistical methods can be applied to the measurements.
The VAS can be compared to other linear scales such as the Likert scale or Borg scale. The sensitivity and reproducibility of the results are broadly very similar, although the VAS may outperform the other scales in some cases. These advantages extend to measurement instruments made up from combinations of visual analogue scales, such as semantic differentials.
VAS is the most common pain scale for quantification of endometriosis-related pain. A review came to the conclusion that VAS and numerical rating scale (NRS) were the best adapted pain scales for pain measurement in endometriosis. For research purposes, and for more detailed pain measurement in clinical practice, the review suggested use of VAS or NRS for each type of typical pain related to endometriosis (dysmenorrhea, deep dyspareunia and non-menstrual chronic pelvic pain), combined with the clinical global impression (CGI) and a quality of life scale.
- U.-D. Reips and F. Funke (2008) "Interval level measurement with visual analogue scales in Internet-based research: VAS Generator." doi:10.3758/BRM.40.3.699
- S. Grant, T. Aitchison, E. Henderson, J. Christie, S. Zare, J. McMurray, and H. Dargie (1999) A comparison of the reproducibility and the sensitivity to change of visual analogue scales, Borg scales, and Likert scales in normal subjects during submaximal exercise. Chest. 116(5):1208-17. doi:10.1378/chest.116.5.1208
- Funke, F; Reips, U.-D. (2012). "Why semantic differentials in Web-based research should be made from visual analogue scales and not from 5-point scales." (PDF). Field Methods 24: 310–327. doi:10.1177/1525822X12444061.
- U.-D. Reips (2006) Web-based methods. In M. Eid & E. Diener (Eds.), Handbook of multimethod measurement in psychology (pp. 73-85). Washington, DC: American Psychological Association. doi:10.1037/11383-006
- Bourdel, N.; Alves, J.; Pickering, G.; Ramilo, I.; Roman, H.; Canis, M. (2014). "Systematic review of endometriosis pain assessment: how to choose a scale?". Human Reproduction Update 21 (1): 136–152. doi:10.1093/humupd/dmu046. ISSN 1355-4786.
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