An Estimator $\hat { \mu } _ { r }$ Of the Population Value

Multiple Choice

An estimator $\hat { \mu } _ { r }$ of the population value $\mu _ { Y }$ is more efficient when compared to another estimator $\tilde { \mu } _ { Y }$ , if

A) $E \left( \hat { \mu } _ { Y } \right) > E \left( \tilde { \mu } _ { Y } \right)$
B) it has a smaller variance.
C) its c.d.f. is flatter than that of the other estimator.
D) both estimators are unbiased, and $\operatorname { var } \left( \hat { \mu } _ { Y } \right) < \operatorname { var } \left( \tilde { \mu } _ { Y } \right)$