The approach louverie and woodworth devloped involved constructing conjoint choice experiments with the use of 2^j designs when there are j possible alternatives , obtained by generating all possible combinations of attribute levels.If there are , for instance , two attributes each with two levels, four alternatives can be constructed. The 2^j design used then contains all combinations of the four alternatives present or absent in the choice set. From the full 2^j design an orthogonal main effects experimental design is selected such that a relatively small number of choice set remains for estimation purposes.A disadvantage of 2^j fractional factorial designs is that when there are many alternatives (J), this approach will result in large tasks for respondents where choice set can contain too many alternatives. A more general version of the 2^j fractional factorial design can be used when each choice set contains a fixed number of alternatives (M) and each alternative has S attributes with each L levels. In that situation a L^m-s main effects, orthogonal, fractional factorial experiment design can be used to create joint combinations of attribute levels.In case the number of levels is not equal for all alternatives a L^m-s design still can be used, where L now represents the maximum number of levels present in the study.
Kartik Singhvi
13082 (Fin Grp-6)
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