将目标总体按某种变量分类后再随机抽取样本的方法是()。 A.随机抽样 B.系统抽样 发布时间:2017-05-25 21:05 │ 来源:www.tikuol.com 题型:单项选择题 问题: 将目标总体按某种变量分类后再随机抽取样本的方法是()。A.随机抽样B.系统抽样C.分组抽样D.分层抽祥
题型:单项选择题 乳腺癌钼靶X线的表现为()A.密度均匀的肿物,边界较清晰、整齐 B.密度均匀的肿物,可见圆圈及小斑片状钙化 C.片状或结节状致密影,和周围腺体组织密度类似 D.高密度影肿物,边缘呈毛刺状,可见小簇状、沙砾样钙化 E.密度不均匀,边界不清楚 查看答案
题型:单项选择题 Questions 1-4What has the man just done during his lunch break?()A.He’s bought his wife a present.B.He’s missed an important phone call.C.He’s dismissed his new secretary.D.He’s popped out shopping. 查看答案