Slider scales and web-based surveys: A cautionary note

Slider scales (or, visual analog scales) are becoming increasingly popular in web-based surveys. These psychometric response scales utilize Likert-type items in which respondents select a point along a line labelled with bipolar endpoints to indicate their preference or agreement with a statement. This article is a response to an article that appeared earlier in the Journal of Research Practice where the writers treated Likert-type data as interval-level measurements. The authors of this response article contend that it is erroneous to suppose the data obtained by visual analog scales to be quantitative and continuous (on an interval scale) when, in fact, these are discreet data (on an ordinal scale), which are essentially qualitative. Qualitative data are not quantitative and no means of analysis can make it so.