<an example of hypergeometric distribution>
here, we have 6 balls. the three of them are red. the rest is blue.
suppose that you take 3 balls of them and that you take one red and two blue without replacement. you can take 3 balls one by one or at the same time.
the total number of the combinations are 6C3.
the number of your taking one red and two blue is 3C1*3C2
therefore, the probability of taking one red and two blue is
3C1*3C2/6C3 = 9/20.
in the first place, in a digression,
hypergeometric consists of hyper and geometric.
hyper means beyond, geometry does figures or tables so hypergeometric does beyond geometry, hard to show in figures or tables.
on the other hand, Poisson distribution is decided by a mean value and can be graphed.