Can someone explain to me how the formula P(X=r) = nCr p^r q^(n-r) (Binomial Distribution)

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Can someone explain to me why combination is used here? I don’t quite understand how this work.

In: Mathematics

2 Answers

Anonymous 0 Comments

Let r = 2 and n = 4.

There are six ways in which two out of the four trials can be successful:

First and second

First and third

First and fourth

Second and third

Second and fourth

Third and fourth

Hence, 4!/(2!2!) = 6.

Make sense?

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