作者piyu (毓)
看板Statistics
标题Re: [问题] 求机率
时间Sun Nov 13 17:29:23 2005
※ 引述《piyu (毓)》之铭言：
: suppose that in the population of twins,male(M)and female(F)
: are equally likely to occur and that twins are identical α
: If twins are not identical,their genes are independent.
: find P(MM)
我的想法如下
︱ m f
──────
m ｜mm mf
f ｜fm ff
P(mm)=P(男-男双胞胎)
=P(男-男双胞胎|基因一样)P(基因一样)+P(男-男双胞胎|基因不一样)P(基因不一样)
1 1
=----α+----(1-α)
4 4
=P(ff)
1
P(mf)=-----(1-α)
2
不过这样P(mm)+P(mf)+P(ff) 不等於一.....那错了呀>"<
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