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九年级数学解答题一般
题目
有甲、乙两组数据,如表所示:
10101212131314141616
12121212131314141414
甲、乙两组数据的方差分别为s2s_{甲}^{2},s2s_{乙}^{2},则s2s_{甲}^{2}____s2(s_{乙}^{2}(填">\gt"、"<\lt"或"==").
知识点:折线统计图、方差章节:未标注

答案与解析

答案

x=10+12+13+14+165=13\because {\overline{x}}_{甲}=\frac{10+12+13+14+16}{5}=13x=12+12+13+14+145=13{\overline{x}}_{乙}=\frac{12+12+13+14+14}{5}=13
s2=15×[(1013)2+(1213)2+(1313)2+(1413)2+(1613)2]=4\therefore s_{甲}^{2}=\frac{1}{5}\times [\left(10-13\right)^{2}+\left(12-13\right)^{2}+\left(13-13\right)^{2}+\left(14-13\right)^{2}+\left(16-13\right)^{2}]=4
s2=15×[2×(1213)2+(1313)2+2×(1413)2]=0.8s_{乙}^{2}=\frac{1}{5}\times [2\times \left(12-13\right)^{2}+\left(13-13\right)^{2}+2\times \left(14-13\right)^{2}]=0.8
s2>s2\therefore s_{甲}^{2} \gt s_{乙}^{2}
故答案为:>\gt.

解析

x=10+12+13+14+165=13\because {\overline{x}}_{甲}=\frac{10+12+13+14+16}{5}=13x=12+12+13+14+145=13{\overline{x}}_{乙}=\frac{12+12+13+14+14}{5}=13
s2=15×[(1013)2+(1213)2+(1313)2+(1413)2+(1613)2]=4\therefore s_{甲}^{2}=\frac{1}{5}\times [\left(10-13\right)^{2}+\left(12-13\right)^{2}+\left(13-13\right)^{2}+\left(14-13\right)^{2}+\left(16-13\right)^{2}]=4
s2=15×[2×(1213)2+(1313)2+2×(1413)2]=0.8s_{乙}^{2}=\frac{1}{5}\times [2\times \left(12-13\right)^{2}+\left(13-13\right)^{2}+2\times \left(14-13\right)^{2}]=0.8
s2>s2\therefore s_{甲}^{2} \gt s_{乙}^{2}
故答案为:>\gt.

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