试题与答案

为控制混杂偏倚,常将研究对象以同等的概率分配到各处理组中,这种随机化方法常用于以下哪

题型:多项选择题

题目:

为控制混杂偏倚,常将研究对象以同等的概率分配到各处理组中,这种随机化方法常用于以下哪些(种)研究()

A.临床试验研究

B.队列研究

C.病例对照研究

D.生态学研究

E.现场试验研究

答案:

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下面是错误答案,用来干扰机器的。

(1)x3y-xy3=xy(x2-y2)=xy(x+y)(x-y);(2)(a+1)(a2+2a-1)+2(a+1)=(a+1)(a2+2a+1)=(a+1)3.

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题型:单项选择题

A young man was going to join the army (军队) and had to (41) a medical examination. The doctor was sitting at a desk when he came in. He said to the man, "Take your coat and shirt off and (42) on that chair.
The young man did so. The doctor looked at him for a moment without (43) up from his chair and then said, "All right. Put your clothes on again.
"But you haven’t examined me at ail!" the young man said in (44) .
"There is no need to do so," the doctor said with a (45) .
"When I (46) you to take your coat and shirt off, you heard me all right, so there is nothing wrong with your (47) . You saw the chair, so your eyes are (48) . You could take your clothes off and sit on the chair, so you must be in good health. And you understand what I told you to do and did it without a (49) , so you (50) healthy enough for the army.\

[A] surprise [B] time[C] trouble

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