Their distinguishing feature is that, when constructing the overall criterion score computed for an alternative and obtained as a convolution of the partial criterion scores, poor values of the partial criterion scores corresponding to some parameters of the alternative are compensated by good values of the partial criterion scores of other parameters of that same alternative. Depending on the way in which poor values of the partial criteria of some parameters of an alternative are compensated by good values of the partial criteria of other parameters of that same alternative, one distinguishes additive strategies of multi-criteria choice, additive-difference strategies, and ideal-point strategies:
- • additive strategy. Its distinguishing feature is as follows. When constructing the overall criterion score, computed for each of the alternatives and taking into account all the partial criteria used that correspond to the analyzed parameters of the alternative, a poor value of one of the partial criteria can be compensated by a good value of other partial criteria. The additive strategy assumes that for each alternative an overall criterion score is determined as the sum of the partial criterion scores, calculated over all the significant parameters of the alternatives, taking into account their relative importance. Here the importance weights of the parameters are either set subjectively or calculated as certain scaled values expressed on a single dimensionless scale. An example is choosing a dacha to buy based on parameters important to the DM (decision maker), such as price, distance from home, availability of public transport, and age of the building. For each of the options (alternatives) under consideration, the DM calculates the overall criterion score as the sum of the products of the actual values of the corresponding parameters for the dacha option (alternative) under consideration and the importance weights of those parameters, set by the DM uniformly for all the options being considered for purchase. In this case, the best option (alternative) will be the one having the greatest value of such an additive score, that is, having the maximum overall utility. Note that the DM does not always compute such a total score (overall criterion score) for each of the alternatives. In general, the method for calculating the overall criterion score can be any method. Thus, the DM may apply simpler estimates, for example, by summing, for each of the alternatives, the number of parameters that are of high importance to the DM. In this case, the alternative chosen will be the one having the greatest number of parameters important to the DM;
- • additive-difference strategy uses pairwise comparisons of alternatives. Here, those parameters of the alternatives that have approximately equal values are excluded from consideration. Pairwise comparison of alternatives on the remaining parameters proceeds as follows: the values of the overall criterion score, now calculated only over the parameters remaining under consideration, are compared. Of the two alternatives being considered, the one retained for further selection is the one that has the greater value of the calculated overall criterion score. The method for calculating the overall criterion score for each of the alternatives also remains compensatory — in the computed generalized score, «poor values» of the partial criteria remaining under consideration can be compensated by «good values» of the remaining partial criteria. Often the DM also disregards those parameters for which the difference in the alternatives' scores is small. In the example considered above, for alternatives having identical values of the parameters «age of the building» and «availability of public transport», only one parameter remains under consideration — «price». Comparing all the alternatives pairwise by the value of this parameter, the DM will, in the end, choose the best alternative, or several having the same, but better, price value. In essence, under this strategy the DM evaluates not the overall utility of each of the alternatives being compared, but the difference between their utilities;
- • ideal-point strategy is similar to the additive-difference strategy, but differs from it in that all the alternatives are compared not with one another, but with a certain benchmark, that is, an ideal option that exists only in the mind and is practically unattainable. Then the best alternative is considered to be the one closest to the «ideal» in terms of the value of the overall criterion score, computed over those parameters whose partial criteria values differ from the values of the ideal alternative. Here, too, the method for calculating the overall criterion score for each of the alternatives remains compensatory.
Note that, depending on the decision-making concept, all alternatives may be considered within the framework of each of these strategies (the utility-maximization concept), or only some of them — up to the appearance of the first alternative that satisfies the DM's aspiration level (the bounded-rationality concept).
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