Hi. I have this problem.

Let Y~binom(n,p) and set \hat{p}=\frac{Y}{n}.You may assume that E(\hat{p})=p and Var(\hat{p})=\frac{p(1-p)}{n}.

a) What is the efficiency of \hat{p} as an estimator of p?

b) Find the Rao-Cramer lower bound for the variance of unbiased estimators of p.

I think i'm okay with part b)

but part a) is what bugging me. What is the efficiency of a binomial of p?