Question 2: What kind of variable are the outcomes in these trials?
These are quantitative scales. Some provide a continuous outcome, such as the visual analogue scales, some a discrete outcome, such as WOMAC and the rating scales.
If you said that they are ordinal scales, you are also correct, they all give an order to levels of pain. We may be reluctant to attach the interval property to them, i.e. to say that differences in pain scores are meaningful, so that the difference in pain between 1 and 2 on a scale is the same as the difference between 3 and 4. However, it would be very difficult to proceed if we did not treat them as quantitative and that is what the auhtors of this paper have done.
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Last updated: 16 February, 2009.