第123页

信息发布者：
D
D
＞
乙
解：
$\overline{x}_甲=\frac{0+1+0+2+2+0+3+1+2+4}{10}=1.5$
$s_甲^2=\frac{1}{10}[(0-1.5)^2+(1-1.5)^2+(0-1.5)^2+(2-1.5)^2+(2-1.5)^2+(0-1.5)^2+(3-1.5)^2+(1-1.5)^2+(2-1.5)^2+(4-1.5)^2]$
$=\frac{1}{10}(2.25+0.25+2.25+0.25+0.25+2.25+2.25+0.25+0.25+6.25)=1.65$
$\overline{x}_乙=\frac{2+3+1+2+0+2+1+1+2+1}{10}=1.5$
$s_乙^2=\frac{1}{10}[(2-1.5)^2+(3-1.5)^2+(1-1.5)^2+(2-1.5)^2+(0-1.5)^2+(2-1.5)^2+(1-1.5)^2+(1-1.5)^2+(2-1.5)^2+(1-1.5)^2]$
$=\frac{1}{10}(0.25+2.25+0.25+0.25+2.25+0.25+0.25+0.25+0.25+0.25)=0.65$
因为$\overline{x}_甲=\overline{x}_乙，$且$s_甲^2＞s_乙^2，$
所以乙机床的性能较好。
8
6和10
8
2.6
60%
8
8
8
1.0
80%
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