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70,75,80,85,90,105,105,130,130,130
the list shown consists of the times, in seconds, that it took each of 10 schoolchildren to tun a distance of 400 meters. if the standard deviation of the 10 running times is 22.4 seconds, rounded to the nearest tenth of a second, how many of the 10 running times are more than 1 standard deviation below the mean of the 10 running times?
a.1
b.2
c.3
d,4
e,5
可以告诉我这道题目是什么意思嘛？方差和标准差的作用是什么，可否有人帮我解读下，因为每次都是第一题，所以很重要，希望高手帮忙。谢谢 |
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发表于 2009-12-22 12:35:02
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