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问题 多项选择题

物料提升机吊笼运行时有抖动现象，请分析故障原因。（）。

A、制动块压得太紧

B、摩擦片、制动轮沾油

C、导轨上有杂物

D、导向滚轮（导靴）和导轨间隙过大

答案

参考答案：C, D

单项选择题

A local elementary school has requested scoliosis screening for its students from the hospital’s community outreach program. The school should be informed that

A. these students are too young to screen; instead, older students should be screened.
B. these students are too old to screen and will no longer benefit from screening for scoliosis.
C. scoliosis screening requires sophisticated equipment and can’t be done in school.
D. this is an appropriate request and arrangements will be made as soon as possibl
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单项选择题 A1型题

两样本均数比较的t检验，t=1.20，α=0.05时统计推断结论为（）

A.两总体均数的差别有统计学意义

B.两样本均数的差别无统计学意义

C.两样本均数的差别有统计学意义

D.两总体均数的差别无统计学意义

E.未给出自由度，无法进行统计推断
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