Browsing by Author "Sarabando, Paula"
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- Approaches to suggest potential agreements: Perspectives of mediation with incomplete informationPublication . Sarabando, Paula; Dias, Luís; Vetschera, RudolfIn bilateral Negotiation Analysis, the literature often co nsiders the case of complete information. In this context, since the negotiators know the value functions of both parties, it is not difficult to calculate the Pareto frontier and the Pareto efficient soluti ons for the negotiation. Thus rational negotiators can reach agreement on this frontier. However, these approaches are not applied in practice when the parties do not have complete information. The research question of our work is “It is possible to help negotiators achieving an efficient soluti on if they do not have complete information regarding the different parameters of the model?”. We propos e to obtain information regarding the preferences of negotiators during the negotiation process , in order to be able to propose alternatives close to the Pareto frontier. During this work we will presen t three approaches to help a mediator proposing a better solution than the compromise the negotia tors have reached or are close to reach.
- Comparison of decision rules to mediate negotiations with incomplete informationPublication . Sarabando, Paula; Dias, LuísDecisions in society resulting from negotiation among two parties are often inefficient (in terms of Pareto efficiency) as the parties fail to identify an agreement that would make both better off. A third party mediating the negotiation can increase the chances of reaching a Pareto efficient alternative. However, in most practical situations the mediator does not have a precise model of the parties’ preferences, and therefore cannot identify which alternatives are efficient. This paper assesses the performance of decision rules that a mediator can apply in multi-issue bilateral negotiation analysis given ordinal information about the importance of the issues and the value of the potential alternatives in each issue. We assume the preferences of the parties can be modelled by an additive multiattribute value function, but without assuming the precise parameters of this model are known. We study three mediation criteria: maximising the sum of the values, maximising the product of the excesses, or maximising the minimal proportion of potential. Monte-Carlo simulation is used to assess how good the alternative chosen by each decision rule is, and to provide guidelines about the use of these rules in a context of selecting a subset of promising alternatives.
- Comparison of different rules to deal with incomplete information: perspectives of mediationPublication . Sarabando, Paula; Dias, LuisIn bilateral Negotiation Analysis, the literature often considers the case with complete information. In this context, since the value (or utility) functions of both parties are known, it is not difficult to calculate the Pareto frontier (or efficient frontier) and the Pareto efficient solutions for the negotiation. Thus rational actors can reach agreement on this frontier. However, these approaches are not applied in practice when the parties do not have complete information. Considering that the additive value (or utility) function is used, often it is not easy to obtain precise values for the scaling weights or the levels’ value in each issue. We compare four decision rules that require weaker information, namely ordinal information on weights and levels, to help a mediator suggesting an alternative under these circumstances. These rules are tested using Monte-Carlo simulation, considering that the mediator would be using one of three criteria: maximizing the sum of the values, maximizing the product of the excesses regarding the reservation levels, or maximizing the minimal proportion of potential. Simulations asses how good is the alternative chosen by each rule, computing the value loss with respect to the alternative that would be suggested if there was precise cardinal information and determining if the chosen alternative is efficient or, if not, how far is the nearest efficient alternative. We also provide guidelines about how to use these rules in a context of selecting a subset of the most promising alternatives, considering the contradictory objectives of keeping a low number of alternatives yet not excluding the best one. A further issue we investigate is whether using only ordinal information leads to treat one of the parties unfairly, when compared to a situation in which precise cardinal values were used instead.
- Information levels in additive group decision models under incomplete information: Bridging the cardinal ordinal gapPublication . Vetschera, Rudolf; Dias, Luís; Sarabando, PaulaIn the literature, several models for group decision making based on the additive aggregation of group members’ utility or value functions have been proposed (Keeney and Kirkwood 1975; Dyer and Sarin 1979; Keeney and Nau 2011). These group aggregation rules usually are based on systems of axioms very similar to those formulated by Arrow (1963) for the case of aggregating ordinal preferences. In contrast to aggregation of ordinal preferences, aggregation of cardinal alues is thus possible in groups. However, it requires group members to specify their preferences in cardinal form, by assigning utility scores to alternatives. This could be difficult for group members, in particular if this information should be provided exactly.
- Levels of incomplete informationin group decision models – A comprehensive simulation studyPublication . Vetschera, Rudolf; Sarabando, Paula; Dias, LuisWe present a comprehensive computational study on the effects of providing different forms of incomplete preference information in additive group decision models. We consider different types of information on individual preferences, and on weights of the group members, and study their effects on conclusiveness, ef fi ciency and fairness of outcomes at the group level. Furthermore, we analyze possible violations of the axiom of independence of irrelevant alternatives (IIA) as well as the impact of problem characteristics, in particular initial agreement between group members. Our results indicate that providing information in the form of a ranking of differences between consecutive alternatives comes close to providing exact cardinal preference information in several outcome dimensions. However, group decision procedures based on incomplete preference information also show a significant amount of violations of the IIA axiom.
- Mediation with Incomplete Information: Approaches to Suggest Potential AgreementsPublication . Sarabando, Paula; Dias, Luís; Vetschera, RudolfIn bilateral Negotiation Analysis, the literature often considers the case of complete information. In this context, since the negotiators know the value functions of both parties, it is not difficult to calculate the Pareto efficient solutions for the negotiation. Thus rational negotiators can reach agreement on this frontier. However, these approaches are not applied in practicewhen complete information is not available. The research question of ourwork is “It is possible to help negotiators achieving an efficient solution in the absence of complete information regarding the different parameters of the model?”. We propose to derive incomplete information about the preferences of negotiators from the statements they make and the offers they exchange during the negotiation process. We present and discuss three approaches that use this information in order to help a mediator proposing a better solution than the compromise the negotiators have reached or are close to reach.
- Modeling consumer preferences for Electric Vehicles: an exploratory studyPublication . Oliveira, Gabriela D.; Dias, Luís C.; Sarabando, PaulaThis paper presents the analysis of c onsumer preferences for Electric Vehicles (EVs), based on the choice within a defined set of vehicles: gasoline, diesel, hybrid, plug- in hybrid or fully electric. The study aims at understanding what the consumer preferences for EVs in Portugal are. The analysis incorporated two methods, Multicriteria Decision Analysis (MCDA) and Conjoint A nalysis. A survey on stated preferences was implemented in order to collect the informa tion required to feed the two methods, from 252 consumers. The criteria selected to charac terize each vehicle (purchase price, range, fuel consumption and CO 2 emissions) were based on a previous survey. The results show that consumers in general are not likely to adopt EVs. Fuel consumption was considered the most relevant criterion, overcoming th e purchase price. Lastly, the existence of privileges for EV owners is not valued as a significant advantage of purchasing an EV.
- Multi-attribute choice with ordinal information: a comparison of different decision rulesPublication . Sarabando, Paula; Dias, LuísIn the context of additive multiattribute aggregation, we address problems with ordinal information, i.e., considering a ranking of the weights (the scaling coefficients). Several rules for ranking alternatives in these situations have been proposed and compared, such as the rank-order-centroid weight, minimum value, central value, and maximum regret rules. This paper compares these rules, together with two rules that had never been studied (quasi-dominance and quasi-optimality) that use a tolerance parameter to extend the concepts of dominance and optimality. Another contribution of this paper is the study of the behavior of these rules in the context of selecting a subset of the most promising alternatives. This study intends to provide guidelines about which rules to choose and how to use them (e.g., how many alternatives to retain and what tolerance to use), considering the contradictory goals of keeping a low number of alternatives yet not excluding the best one. The comparisons are grounded on Monte Carlo simulations.
- A Note on a Group Preference Axiomatization with Cardinal UtilityPublication . Dias, Luís; Sarabando, PaulaKenneth Arrow’s work on social welfare proposed a set of conditions that a function to aggregate ordinal preferences of the members of a group should satisfy, proving that it was not possible to satisfy all these assumptions simultaneously. Later, Ralph Keeney adapted these conditions and proposed a cardinal utility axiomatization for the problem of aggregating the utility functions. This note discusses in particular the condition of nondictatorship. It proposes stronger formulations for this condition to limit the maximum influence that an individual can have, and it presents the corresponding characterization of compliant group cardinal utility functions. An extension to address coalitions of individuals acting strategically is also discussed.
- On a Group Preference Axiomatization with Cardinal UtilityPublication . Dias, Luís; Sarabando, PaulaArrow proposed a set of conditions for a function to aggregate ordinal preferences of the members of a group, proving that it was not possibl e to satisfy all these assumptions simultaneously. Later, Keeney adapted these conditions and proposed a cardinal utility axiomatization for the problem of aggregating the utility functions. This work dis cusses the condition of nondictatorship. It propose s a stronger formulation for this condition and prese nts the corresponding characterization of group cardinal utility functions.