Assume a family is planning to have three children.

Question

1. Why do probabilities centered around this scenario represent the same probabilities as those for flipping three coins

Answer 1

mmmh,

in flipping one coin, and having one child:
prob(heads) = 1/2, prob(tails) = 1/2
prob(boy) = 1/2 , prob (girl) = 1/2

for flipping 3 coins, or considering 3 kids:
prob(1 head, 2 tails) = 3(1/2)^3 = 3/8
prob(1 boy, 2 girls) = 3(1/2)^3 = 3/8

etc.

Answer 2

This is because each pregnancy is independent of the others so the chances of receiving either a boy or girl is 50% for each separate pregnancy. the same as flipping three coins, the chances of having either heads or tails is 50% and each flip is independent of the others.