Visual Analog Survey Scale
The Visual Analog Scale (VAS) is one such combination scale presentation, developed by Hayes and Patterson in 1921. It was created for use in hospitals where pain levels need to be assessed quickly with patients who might not understand the local language.
Here’s the concept. The patient is shown a sheet of paper with a 100 mm horizontal line where one end of the line represents no pain and the other end extreme pain. Ask the patient to indicate how much pain they’re feeling by marking a place along the line. The distance to the mark is measured, and voila, we have a measurement on a 0 to 100 scale.
- Why is this “visual”? Visual is an odd term here. “Linear” might be better. Arguably, ideographs are “visual.” The line as the “visual” representation of the scale makes this, well, visual. On a webform, it would be a slider.
- What makes this “analog”? Analog means “continuous” – as opposed to “discrete”. Verbal, numerical, and ideographic scale representations have distinct, individual points to the scale. For example: 1, 2, 3, 4 and 5. That makes these scale types discrete. (And I don’t mean “discreet”!) The longest discrete scale commonly used is a 0-to-10 scale – all of 11 points! — for the Net Promoter Score measurement.
A line (or slider) technically has an infinite number of points on it. That’s continuous or analog.
- Why use an analog or visual scale? The argument for a visual scale: it’s more precise. Think about final exams in school. You were graded on a 100-point scale. An 89 (B+) was different from an 91 (A-). So, the 100-point scale was a more precise reflection of your grasp of the material that a 10-point scale would be.
While an analog scale has an infinite number of points on it, whatever point the respondent chooses is usually coded as a 0-to-100 scale. While we could be more precise and measured to the 10th of a millimeter, at some point we simply have “false precision.