Question

For binomial distribution: E[X] = n(pi) and variance is n(pi)(1-pi). How do i prove variance?

Answer 1

really the same technique as deriving the the mean

Answer 2

compute \[\mathbf{E} [X(X-1)]\]

Answer 3

E[X^2 - X] = E[X^2] - E[X?]

Answer 4

and then expand from there?

Answer 5

compute it using the pdf of the binomial

Answer 6

of pmf if you prefer that notation

Answer 7

Ok. Thank you very much. I shall keep that in mind in todays exam