How we change what others think, feel, believe and do
Visual-Analog Rating scale
The visual-analog rating scale displays a scale as a blank line, without any choices. An extreme alternative is described at either end of the line and the person must choose somewhere in between the two, marking the point with an 'X'. A center point may be marked.
Analysis of results is done by grouping markings by applying an 'overlay'. Physically, this could be a clear plastic sheet that is laid on top of question page with a Likert-style limited number of sections, for example four or five.
When you think about your experiences over the past day, on the whole, how do you feel (Please put a X on the line):
Very unhappy |_______________|_______________| Very happy
The problem with a set of choices, such as in the Likert scale, is that any words are liable to quite variation in interpretation and hence scoring. For example some people may consider 'quite happy' as meaning very happy, whilst others may see it as only slightly happy.
A common strategy will be to mark questions relatively to one another, thus 'I'll put the X more to the right on this one as compared with the previous one as I feel more strongly about this'.
The visual-analog scale does away with word-interpretation errors by presenting a simple line. A center mark on the scale helps the person deliberately lean one way or another.
There are still potential problems with this method, for example that people become uncertain and so place their 'X' relatively randomly. There is also the question of what to do when people deliberately place marks relative to one another to show comparative choice, but the overlay lumps them all into one or a few categories.
This method can be more effort to select and analyze data and the choice of where to segment the overlay can lead to very different results. Often this is done with a simple division across the line width. Divisions could also be set with, for example, a measurement of standard deviation or quartiles based on a study of a random sample of responses.
The method also works better on paper -- it is difficult to offer an analog choice on a computer screen.
The visual analog scale is also known as a Graphic Rating scale as it uses a visual format with a metaphor of distance and relative position to represent importance.