suppose that X ~ Bin(n, p)
a. show that E(X^k)=npE((Y+1)^(k-1)) where Y ~ Bin(n-1, p)
b. use part (a) to find E(x^2)
where Y ~ B(n-1 , p)
So using this , E (X2) = np E( Y+1)
So,
( because sum of probability of all values of random variable =1)
Mean of a random variable ~ B(n,p) = E(X) = np
this implies
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