Posted by **Chelsea** on Saturday, May 28, 2011 at 8:44pm.

Supposed (as is roughly correct) that each child born is equally likely to be a boy or a girl and that sexes of successive children are independent. If we let BG mean that the older child is a boy, and the younger child is a girl, then each of the combinations BB, BG, GB, GG has probability 0.25. Ashley and Brianna each have two children.

a.) You know that at least one of Ashley's children is a boy. What is the conditional probability that she has two boys?

b.) You know that Brianna's older child is a boy. What is the conditional probability that she has two boys?

please help, if you can :)

- Statistics -
**Mgraph**, Sunday, May 29, 2011 at 11:11am
The formula of the conditional probability

P(X\Y)=P(XY)/P(Y)

a)Y="at least one is a boy"

Y=BB+BG+GB, P(Y)=3/4

X=BB

If X then Y => XY=X P(XY)=P(X)=1/4

P(X\Y)=(1/4)/(3/4)=1/3

b)Y="the older child is a boy"

Y=BB+BG, P(Y)=1/2

X=BB, XY=X, P(XY)=1/4

P(X/Y)=(1/4)/(1/2)=1/2

## Answer this Question

## Related Questions

- odds of... - Does anyone know the odds of having Two girls as children as ...
- Math - In a family with two children, what are the probabilities of the ...
- probability - For a family with 2 children, the sample space indicating boy (B) ...
- math - Assuming boy and girl babies are equally likely, find the probability ...
- statistics - If boys and girls are equally likely to be born, what is the ...
- math - in a family with two children, what are the probabilities of two boys, ...
- Math - In a family with two children, what are the probabilities of the ...
- math - Suppose that China’s population policy is modified so that every family ...
- Math - If boys and girls are equally likely to be born, what is the probability ...
- Probability - We are given the following statistics about the number of ...