题型:填空题 Each of us has to write a ______ report every two weeks. A. two-hundred-word B. two-hundreds-word C. two-hundred-words 查看答案
题型:填空题 正常人的脉搏平均为72(次/分钟)。某职业病院测得10例慢性四乙基铅中毒者的脉搏(次/分钟)为:54,67,68,70,66,67,70,历,69,78。问四乙基铅中毒者的脉搏与正常人的有无显著性差异已知四乙基铅中毒者的脉搏服从正态分布这组样本的标准差()A.5.63B.5.93C.72D.5.632E.5.932 查看答案