变异系数如何应用?
参考答案:
①比较均值相差悬殊的几组资料的变异度;②比较度量衡单位不同的多组资料的变异度;③变异系数还常用于比较多个样品重复测定的误差。
—This pair of shoes belong to Jack. He likes this kind very much.
—It __ be his. It's too large for him. [ ]
A. can; can't
B. may; needn't
C. must; mustn't
D. must; can't
下列有关急性筛窦炎的临床特点,错误的是()。
A.鼻塞
B.多脓涕
C.头痛或局部疼痛
D.头痛部位在眶上额部
E.后组筛窦炎疼痛位于枕部