Definition: The Paired Comparison Scaling is a comparative scaling technique wherein the respondent is shown two objects at the same time and is asked to select one according to the defined criterion. The resulting data are ordinal in nature.
The paired Comparison scaling is often used when the stimulus objects are physical products. The comparison data so obtained can be analyzed in either of the ways. First, the researcher can compute the percentage of respondents who prefer one object over another by adding the matrices for each respondent, dividing the sum by the number of respondents and then multiplying it by 100. Through this method, all the stimulus objects can be evaluated simultaneously.
Second, under the assumption of transitivity (which implies that if brand X is preferred to Brand Y, and brand Y to brand Z, then brand X is preferred to brand Z) the paired comparison data can be converted into a rank order. To determine the rank order, the researcher identifies the number of times the object is preferred by adding up all the matrices.
The paired comparison method is effective when the number of objects is limited because it requires the direct comparison. And with a large number of stimulus objects the comparison becomes cumbersome. Also, if there is a violation of the assumption of transitivity the order in which the objects are placed may bias the results.