题干

某中学开展演讲比赛活动,九(1)、九(2)班根据初赛成绩各选出5名选手参加复赛,两个班各选出的5名选手的复赛成绩(满分为100分)如图所示.

(1)根据右图,分别求出两班复赛的平均成绩和方差;

(2)根据(1)的计算结果,分析哪个班级的复赛成绩比较稳定.

上一题 下一题 0.0难度 选择题 更新时间:2018-10-26 12:41:27

答案(点此获取答案解析)

解:(1)九(1)班的选手的得分分别为85,75,80,85,100,

∴九(1)班的平均数=(85+75+80+85+100)÷5=85,

九(1)班的方差S12=(85﹣85)2+(75﹣85)2+(80﹣85)2+(85﹣85)2+(100﹣85)2÷5=70;

九(2)班的选手的得分分别为70

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