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In game theory, strategic dominance (commonly called simply dominance) occurs when one strategy is better than another strategy for one player, no matter how that player's opponents may play. Many simple games can be solved using dominance. The opposite, intransitivity, occurs in games where one strategy may be better or worse than another strategy for one player, depending on how the player's opponents may play. ==Terminology== When a player tries to choose the "best" strategy among a multitude of options, that player may compare two strategies A and B to see which one is better. The result of the comparison is one of: * B dominates A: choosing B always gives as good as or a better outcome than choosing A. There are 2 possibilities: * * B strictly dominates A: choosing B always gives a better outcome than choosing A, no matter what the other player(s) do. * * B weakly dominates A: There is at least one set of opponents' action for which B is superior, and all other sets of opponents' actions give B the same payoff as A. * B and A are intransitive: B neither dominates, nor is dominated by, A. Choosing A is better in some cases, while choosing B is better in other cases, depending on exactly how the opponent chooses to play. For example, B is "throw rock" while A is "throw scissors" in Rock, Paper, Scissors. * B is dominated by A: choosing B never gives a better outcome than choosing A, no matter what the other player(s) do. There are 2 possibilities: * * B is weakly dominated by A: There is at least one set of opponents' actions for which B gives a worse outcome than A, while all other sets of opponents' actions give A the same payoff as B. (Strategy A weakly dominates B). * * B is strictly dominated by A: choosing B always gives a worse outcome than choosing A, no matter what the other player(s) do. (Strategy A strictly dominates B). This notion can be generalized beyond the comparison of two strategies. * Strategy B is strictly dominant if strategy B ''strictly dominates'' every other possible strategy. * Strategy B is weakly dominant if strategy B ''dominates'' all other strategies, but some (or all) strategies are only ''weakly dominated'' by B. * Strategy B is strictly dominated if some other strategy exists that strictly dominates B. * Strategy B is weakly dominated if some other strategy exists that weakly dominates B. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Strategic dominance」の詳細全文を読む スポンサード リンク
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