A family has two children; record the genders in order of birth.
A){BB,BG,GG},equally likely
B){BB,BG,GB,GG},equally likely
C){BB,BG,GG},not equally likely
D){BB,BG,GB,GG},not equally likely
E){B,G},equally likely

Question

Quizplus · Accepted Answer

This is the classic setup for a family with two children, in which each child can be either a boy (B) or a girl (G). There are four possible outcomes: BB (both boys), BG (one boy and one girl), GB (one girl and one boy), and GG (both girls). Each of these outcomes is equally likely.

Choice A is incorrect because it only includes three possible outcomes, when there are actually four.

Choice C is incorrect because it assumes that having a boy or a girl first is equally likely, when in fact the probability of having a boy or a girl first is always 1/2.

Choice D is incorrect because it includes GB and BG as separate outcomes, even though they are the same result (one girl and one boy).

Choice E is incorrect because it only lists the genders without considering the order of birth.

A Family Has Two Children; Record the Genders in Order