答案的这句话没看懂

问题如下：

The variance of sample mean is smallest of all unbiased estimators, which of the following can describe this properity ?

选项：

A.

The estimator is efficient.

B.

The estimator is consistent.

C.

The estimator is accuracy.

解释：

A is correct

If an estimator's variance of sampling distribution is smallest of all unbiased estimators , the estimator is viewed as efficient.

如果一个估计量的抽样分布的方差在所有无偏估计量中是最小的，则该估计量会被视为有效的估计量。