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Behav Res Methods. 2008 Aug;40(3):699-704.

Interval-level measurement with visual analogue scales in Internet-based research: VAS Generator.

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University of Zürich, Zürich, Switzerland.


The present article describes VAS Generator (, a free Web service for creating a wide range of visual analogue scales that can be used as measurement devices in Web surveys and Web experimentation, as well as for local computerized assessment. A step-by-step example for creating and implementing a visual analogue scale with visual feedback is given. VAS Generator and the scales it generates work independently of platforms and use the underlying languages HTML and JavaScript. Results from a validation study with 355 participants are reported and show that the scales generated with VAS Generator approximate an interval-scale level. In light of previous research on visual analogue versus categorical (e.g., radio button) scales in Internet-based research, we conclude that categorical scales only reach ordinal-scale level, and thus visual analogue scales are to be preferred whenever possible.

[Indexed for MEDLINE]

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