题干

某企业为了了解职工的工作状况,随机抽取了一个车间对职工工作时间的情况进行暗访,工作时间在 8.0 小时及以上的为合格.把所得数据进行整理后,分成 6 组画出频率分布直方图(如图所示),但由于工作疏忽,没有画出最后一组,只知道最后一组的频数是 7 .
 
(Ⅰ)求这次暗访中工作时间不合格的人数;
(Ⅱ)已知在工作时间超过 10.0 小时的人中有两名女职工,现要从工作时间在 10.0 小时以上的人中选出两名代表在职工代表大会上发言,求至少选出一位女职工作代表的概率.
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解:(Ⅰ) ∵ 第 6 组的频率为 1−(0.04

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