单选题 Which of the following statistical properties is most accurate if an estimator becomes more accurate as the sample size increases?
A. unbiased.
B. efficient.
C. consistent.

【正确答案】 C

【答案解析】[解析] 估计的理想统计特性包括无偏性(unbiased)、有效性(efficient)和一致性(consistent)。无偏性是指估计的误差是随机的；有效性是指比任何其他无偏估计值的标本误差更小；而一致性是指标本误差的方差值随着标本数目的增加而减少。