MHB Probability distribution of girls

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The discussion revolves around determining the probability distribution of the number of girls (X) in a family with four children, where each child can equally be a boy or a girl. There are 16 possible outcomes for the combinations of boys and girls, not just five, because each child represents a binary outcome (boy or girl), leading to 2^4 combinations. The probability of having k girls can be calculated using the binomial probability formula, where n equals 4 and p equals 1/2. The outcomes are not equally likely when considering the number of girls, as having one girl is more probable than having none. Understanding these probabilities helps clarify the distribution of girls in families with multiple children.
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A certain couple is equally likely to
have either a boy or a girl. If the family has four children, let X
denote the number of girls.

Determine the probability distribution of X. (Hint: There are
16 possible equally likely outcomes. One is GBBB, meaning
the first born is a girl and the next three born are boys.)

=============

i don't understand why there are 16 outcomes not 5.
there can be 0, 1, 2, 3, or 4 girls..
 
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Yuuki said:
A certain couple is equally likely to
have either a boy or a girl. If the family has four children, let X
denote the number of girls.

Determine the probability distribution of X. (Hint: There are
16 possible equally likely outcomes. One is GBBB, meaning
the first born is a girl and the next three born are boys.)

=============

i don't understand why there are 16 outcomes not 5.
there can be 0, 1, 2, 3, or 4 girls..

The formula for probability of 'k over n' events is...

$\displaystyle P_{k,n} = \binom {n}{k} p^{k}\ (1-p)^{n - k}\ (1)$

... where $\displaystyle \binom {n}{k} = \frac{n!}{k!\ (n-k)!}$. In your case is $n=4$ and $p= \frac{1}{2}$ so that...

Kind regards

$\chi$ $\sigma$
 
Yuuki said:
i don't understand why there are 16 outcomes not 5.
there can be 0, 1, 2, 3, or 4 girls..

The problem is that those outcomes are not equally likely.

Each child can either be a boy or a girl.
Those 2 outcomes are equally likely.

If we look at only 2 children, the outcomes that are equally likely are BB, BG, GB, GG.
As you can see the outcome of 1 girl is twice as likely as 0 girls.

In the case of 4 children, what would be the probability of 0 girls?
 
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