If there are two unbiased estimators of a parameter,the one whose variance is smaller is said to be relatively efficient.

Unbiased Estimators

Statistical estimators whose expected value is equal to the parameter being estimated.

Variance

A measure of the dispersion indicating how much the values in a data set differ from the mean.

Relatively Efficient

Describes a statistical estimator or procedure that has lower variance or better performance compared to others under certain conditions.