I know the unconditional variance formula of the form:

((n)(r)(N-r)(N-n)) / ((N)(N)(N-1))

So, what is the variance formula conditioned on 1 or 2 items - particularly when there's 3 different items to choose from ?

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- Nov 17th 2012, 02:34 AMTheCountadorHypergeometric conditional variance formula
I know the unconditional variance formula of the form:

((n)(r)(N-r)(N-n)) / ((N)(N)(N-1))

So, what is the variance formula conditioned on 1 or 2 items - particularly when there's 3 different items to choose from ? - Nov 17th 2012, 03:26 PMchiroRe: Hypergeometric conditional variance formula
Hey TheCountador.

Consider finding the random Z where Z is the distribution when conditioned and then get Var[Z] = E[Z^2] - E[Z]^2 using standard formulae.