I have 16 marbles: 5 red, 11 blue.
I want to know the probability of getting 2 red and 2 blue when four are picked.
For the binomial I have:
which gives: . . ← This is incorrect.
Now for the combination: .
Don't understand why they have different answers.
Using the Binomial formula, the events are independent.
You are drawing the four marbles with replacement.