Interval-level measurement with visual analogue scales in Internet-based research: VAS Generator.
The present article describes VAS Generator (www.vasgenerator.net), 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.
Reips
Ulf-Dietrich
UD
University of Zürich, Zürich, Switzerland. u.reips@psychologie.uzh.ch
Funke
Frederik
F
D006801:Humans; D020407:Internet / Q000295:instrumentation*; D010775:Photic Stimulation / Q000295:instrumentation; D012106:Research / Q000295:instrumentation*; D011795:Surveys and Questionnaires