偏好男孩但一直生到男孩：社会男孩比例
Primitive Preference
题目详情
在某社会中，每对夫妻都偏好男孩，并且会一直生孩子直到生出男孩为止，然后停止生育。假设每次生男/女的概率均为 1/2 且相互独立。
问：长期来看，这个社会中新生儿中男孩比例会趋于多少？
On Earth II, every couple prefers to have a baby boy over a baby girl. Assume that there is an equally likely chance of having a boy or girl, and that the genders of children are mutually independent. If each couple continues on having more children until they have a boy, in which they will stop having more children, what does the percentage of boys in this society approach over time?
解析
每次出生的性别仍是独立且男/女各 1/2，因此长期男孩比例趋于 50%。
Original Explanation
The percentage of boys in this society is dependent on nature, not on couples' preferences. Every newborn child has an equal probability of being either a boy or a girl, regardless of the gender of any other children. Thus, the percentage of boys in this society approaches .