题干

 某县八年级有3000名学生参加“爱我中华知识竞赛”活动.为了了解本次知识竞赛的成绩分布情况,从中随机抽取了部分学生的得分进行统计.请你根据不完整的表格,解答下列问题:

成绩 x 分频 数频 率
50≤x<6010
60≤ x <70160.08
70≤ x <80
0.2
80≤ x <90620.31
90≤ x <100720.36

 
(1)补全频数分布表;
(2)随机抽取的样本容量为         
(3)若将得分转化为等级,规定50≤x<60评为“D”,60≤x<70评为“C”,70≤x<90评为“B”,90≤x<100评为“A”.估计这3000名学生中,有多少学生得分等级为A?

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答案(点此获取答案解析)

解:(1)70≤x<80分数段的频数40(人),
50≤x<60分数段频率为0.05;
(2)200
(3)根据题意得:3000×0.36=1080,
所以这3000名学生中,有1080名学生得分等级为A.

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