两人分一笔总数固定的钱,比如100元。方法是:A提出方案,B表决。如果后者同意,则按照方案分,如果后者反对,则两人将一无所。
在R软件中有一个 games 包可以建立这个模型,步骤如下:
> library(games)
> data(student_offers)
数据结构如下:
> head(student_offers)
offer accept gender1 gender2
1 20 0 0 0
2 49 0 0 0
3 10 0 0 0
4 1 0 0 0
5 21 0 0 0
6 50 1 1 0
变量 offer 是A所提分给B多少钱的方案;变量 accept 代表 B 是否接受,1 代表接受,0代表拒绝; gender1 为1时代表A是女性,0为男性;gender2为1时代表B是女性,0为男性。
模型图:
建立模型:
> stu1 <- ultimatum(offer + accept ~ gender1 | gender2, data = student_offers,
+ maxOffer = 100, s2 = 1)
诊断模型:
> profstu1 <- profile(stu1, which = 1:4)
Estimating likelihood profiles...
======================================================================
警告信息:
In profile.game(stu1, which = 1:4) :
some profiled fits have higher log-likelihood than original fit; refit the model using "profile" option
> plot(profstu1)
优化效果有待提高,修正模型:
> stu2 <- update(stu1, profile = profstu1)
结果:
> stu2
A fitted strategic model
CALL:
ultimatum(formulas = offer + accept ~ gender1 | gender2, data = student_offers,
maxOffer = 100, s2 = 1, profile = profstu1)
COEFFICIENTS:
Player 1's reservation value:
(Intercept) 76.1977
gender1 -25.5591
Player 2's reservation value:
(Intercept) 45.5045991
gender2 -0.5473444
Logged scale parameter for player 1:
estimated as 3.329319
Logged scale parameter for player 2:
fixed to 0
也就公式:
A的期望收益:R1 = 76.2 - 25.56 * gender1
B的期望收益:R2 = 45.5 - 0.55 * gender2
说明男性比女性有更强的自尊心。A是男性大多给女性分24元,女性也会同意,而女性大多要分一半给B,而B不管是男性还是女性基本上都能得到45元左右。