甲、乙两名战士在相同条件下各射靶10次,每次命中的环数分别是: 甲:8 6 7 8 6 5 9 10 4 7 乙:6 7 7 8 6 7 8 7 9 5 (1)分别计算以上两组数据的平均数; (2)分别求出两组数据的方差; (3)根据计算结果,估计两名战士的射击情况. |
(1)=(8+6+…+7)=7(环) =(6+7+…+5)=7(环) (2)S甲2=[(8-7)2+(6-7)2+…+(7-7)2]=3(环2), S乙2=[(6-7)2+(7-7)2+…+(5-7)2]=1.2(环2), (3)从平均数看甲﹑乙两名战士的成绩相同.从看方差乙的方差较小,乙的射击成绩较稳定.综上乙射击成绩较好. |
核心考点
试题【甲、乙两名战士在相同条件下各射靶10次,每次命中的环数分别是:甲:8 6 7 8 6 5 9 10 4 7乙:6 7 7 8 6 7】;主要考察你对
数字特征等知识点的理解。
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举一反三
数据x1,x2,…,x8平均数为6,标准差为2,则数据2x1-6,2x2-6,…,2x8-6的平均数为______,方差为______ |
从某项综合能力测试中抽取100人的成绩,统计如下表,则这100人成绩的平均数为______.
分数 | 5 | 4 | 3 | 2 | 1 | 人数 | 20 | 10 | 30 | 30 | 10 | 根据台湾寿险业的资料,男性从0岁、1岁、…到60岁各年龄层的死亡率 (单位:%)依序为 1.0250,0.2350,0.1520,0.1010,0.0720,0.0590,0.0550,0.0540,0.0540,0.0520, 0.0490,0.0470,0.0490,0.0560,0.0759,0.1029,0.1394,0.1890,0.2034,0.2123, 0.2164,0.2166,0.2137,0.2085,0.2019,0.1948,0.1882,0.1830,0.1799,0.1793, 0.1813,0.1862,0.1941,0.2051,0.2190,0.2354,0.2539,0.2742,0.2961,0.3202, 0.3472,0.3779,0.4129,0.4527,0.4962,0.5420,0.5886,0.6346,0.6791,0.7239, 0.7711,0.8229,0.8817,0.9493,1.0268,1.1148,1.2139,1.3250,1.4485,1.5851, 1.7353. 经初步整理后,已知61个资料中共有24个资料小于0.2.请问死亡率资料的中位数为下列哪一个选项? (1)0.2034 (2)0.2164 (3)0.2137 (4)0.2085 (5)0.2019. | 春节期间,小乐对家庭中的六个成员收到的祝福短信数量进行了统计:
家庭成员 | 爷爷 | 奶奶 | 爸爸 | 妈妈 | 姐姐 | 小乐 | 收到短信数量x | 42 | 16 | 220 | 140 | 350 | a | 已知总体的各个体的值由小到大依次为2,3,3,7,a,b,12,13.7,18.3,20,且总体的中位数为10.5.若要使该总体的方差最小,则a、b的取值分别是a=______,b=______. |
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