Hiya guys, thanks in advance
There are 15children in a class
1)what is the probability that i)0 ii)1 iii)2 iiii) at least 3 were born in january.
Thank you
Let $\displaystyle p$ be the probability of a child who were born in January; $\displaystyle q$ be the probability of a child who were NOT born in January.
It is easy to see that $\displaystyle p=\frac{1}{12}$ and $\displaystyle q=\frac{11}{12}$
According to the Binomial Distribution: $\displaystyle p(y)=\binom{n}{y}p^yq^{n-y}$
Here we have $\displaystyle n=15$, for (i), (ii) and (iii), you can let $\displaystyle y=0$, $\displaystyle y=1$ and $\displaystyle y=2$ respectively.
Note for (iv), you can find the probability by $\displaystyle p(y\ge 3)=1-p(y\le 2)$
Roy