问题 单项选择题

某企业生产大米,包装标准是每包大米100斤。假定每包大米的重量服从正态分布,且标准差为2,则在95.45%的包装中大米重量的取值范围是()。

A.(100-4,100+4)

B.(100-2,100+2)

C.(100-6,100+6)

D.(100-8,100+8)

答案

参考答案:A

解析:

我们以95.45%的置信水平推断总体参数μ的置信区间时,约有两个标准差的区间会包括μ。此时包装中大米重量的取值范围为,结果即A。

改错题

单句改错.

1. You must practice a lot of if you want to be good at hosting.        
                        A          B                C                   D                                
2. I had much work to be done, so I was very busy.                      
               A                    B         C     D                                            
3. Remember to listen and write in the same time, will you?              
          A              B                   C                            D                              
4. I hear many people donated money for Save China's Tigers in the show.
        A                B        C                   D                                          
5. A microphone makes your voice to sound louder.                        
                              A               B        C          D                                    _____
      

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单项选择题