有十个数 70 75 80 85 90 105 105 130 130 130 The list consists of the times, in seconds, that it took each of 10 schoolchildren to run a distance of 400 meters. If the standard deviation of 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? 选项有 1， 2 ， 3， 4， 5 诚心求教，谢谢各位了
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发表于 2010-5-18 10:51:19
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