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一个单位共有职工200人,其中不超过45岁的有120人,超过45岁的有80人.为...
一个单位共有职工200人,其中不超过45岁的有120人,超过45岁的有80人.为了调查职工的健康状况,用分层抽样的方法从全体职工中抽取一个容量为25的样本,应抽取超过45岁的职工 人.
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1、F
2是椭圆的两个焦点,满足
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B.(0,
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C.(0,
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“x≠3或y≠5”是“xy≠15”的( )
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以半径为1的圆内任一点为中点作弦,则弦长超过圆内接等边三角形边长的概率是( )
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D.
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D.
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若已求得它们的回归直线方程的斜率为6.5,这条回归直线的方程为( )
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