用均数和标准差可全面描述哪项资料的特征（）
A.对称分布
B.负偏态分布
C.正态和近似正态分布
D.正偏态分布
E.分布不明
参考答案：C
The least accurate statement about measures of dispersion for a distribution is that the:（）
A. range provides no information about the shape of the data distribution.
B. mean absolute deviation will always be smaller than the standard deviation.
C. arithmetic average of the deviations around the mean will always be equal to one.
以下哪一项不是常用的调剂工具( )
A．戥称 B．分厘戥 C．研钵 D．铁碾船 E．天平
