完全資訊

完全資訊（粵拼：jyun4 cyun4 zi1 seon3；英文：perfect information）喺經濟學同博弈論上係指一個所有個體都知嗮所有所需資訊嘅情況，喺某啲經濟模型當中會用到。

不完全資訊（英文：imperfect information）就係指個個體唔係知道嗮所需資訊嘅情況。

概論

好似德州話事啤噉就係不完全資訊遊戲－玩家唔知對方有咩牌喺手。

喺有完全資訊嘅博弈當中，所有博弈者都完美知道嗮之前嘅博弈者做過嘅決策。好多圖板遊戲都係完全資訊博弈，例如係象棋－喺象棋當中，每個玩家都可以知嗮對手同自己之前做過咩決策，所以具有完全資訊，而對完全資訊嘅分析喺對圖板遊戲嘅研究好有用^[1]^[2]^[3]。不完全資訊博弈就包括啤牌同埋橋牌等等，喺德州話事啤（Texas hold'em）入面，每個牌手喺一局開始嗰時會獲派兩張啤牌，而呢兩張牌係乜唔到最後都唔會揭曉，牌手頂櫳都只係有得憑對手嘅行為估對手有乜牌^[4]^[5]。

想像下面嗰幅決策樹所描述嘅一場序貫博弈（以擴展形式表達），規則如下：兩個博弈者先後做決策，而每個結果會有若干報償；博弈者 1 先做決策，而且博弈者 2 冇方法直接得知佢揀咗乜；博弈者 1 手上有三個選項，C、D、同 O，如果佢揀咗 O，會令到博弈者 2 冇得做決策，並且直接造成（2, 2）嘅報償，其他可能結果嘅報償如圖所示。假如家吓博弈者 2 俾人叫佢做決策，假設博弈者 2 清楚博弈規則，就算冇人話佢知博弈者 1 揀咗乜，佢都會有能力推斷博弈者 1 實冇揀 O，但佢冇得知到底博弈者 1 揀咗 C 定 D－所以呢場博弈具有不完全資訊^[6]。

睇埋

攷

↑ Gale, D., & Stewart, F. M. (1953). Infinite games with perfect information. Contributions to the Theory of Games, 2, 245-266.
↑ Mycielski, J. (1992). Games with perfect information. Handbook of game theory with economic applications, 1, 41-70.
↑ Reny, P. J. (1988, January). Common knowledge and games with perfect information. In PSA: Proceedings of the Biennial Meeting of the Philosophy of Science Association (Vol. 1988, No. 2, pp. 363-369). Philosophy of Science Association.
↑ Owen, Guillermo (1995). Game Theory: Third Edition. Bingley: Emerald Group Publishing. p. 4.
↑ Brown, N., & Sandholm, T. (2017). Safe and nested subgame solving for imperfect-information games. In Advances in Neural Information Processing Systems (pp. 689-699).
↑ Kreps, D. M., & Wilson, R. (1982). Reputation and imperfect information. Journal of economic theory, 27(2), 253-279.

拎

11.4 Reasoning with Imperfect Information.

[1] Gale, D., & Stewart, F. M. (1953). Infinite games with perfect information. Contributions to the Theory of Games, 2, 245-266.

[2] Mycielski, J. (1992). Games with perfect information. Handbook of game theory with economic applications, 1, 41-70.

[3] Reny, P. J. (1988, January). Common knowledge and games with perfect information. In PSA: Proceedings of the Biennial Meeting of the Philosophy of Science Association (Vol. 1988, No. 2, pp. 363-369). Philosophy of Science Association.

[4] Owen, Guillermo (1995). Game Theory: Third Edition. Bingley: Emerald Group Publishing. p. 4.

[5] Brown, N., & Sandholm, T. (2017). Safe and nested subgame solving for imperfect-information games. In Advances in Neural Information Processing Systems (pp. 689-699).

[reput-6] Kreps, D. M., & Wilson, R. (1982). Reputation and imperfect information. Journal of economic theory, 27(2), 253-279.

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