What are the advantages and disadvantages of the direct and derived approaches to obtaining perception data for multidimensional scaling?

What will be an ideal response?

Direct approaches have the advantage that the researcher does not have to identify a set of salient attributes. Respondents make similarity judgments using their own criteria, as they would under normal circumstances. The disadvantages are that the criteria are influenced by the brands or stimuli being evaluated. If the various brands of automobiles being evaluated are in the same price range, then price will not emerge as an important factor. It may be difficult to determine before analysis if and how the individual respondents' judgments should be combined. Furthermore, it may be difficult to label the dimensions of the spatial map. The advantage of the attribute-based approach is that it is easy to identify respondents with homogeneous perceptions. The respondents can be clustered based on the attribute ratings. It is also easier to label the dimensions. A disadvantage is that the researcher must identify all the salient attributes, a difficult task. The spatial map obtained depends upon the attributes identified.