prep一道数学题 求高手

orangerecord

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 run a distance of 400 meters. If the standard deviation of the 10 running times is 22.4 seconds, rounded to nearest tenth of a second, how many of the 10 running times are more than 1 standard deviatoion below the mean of the 10 running times? (最后一句话就没读懂)

One
Two
Three
Four
Five

wanglechinausa

我不太懂哈，我试试。首先求出平均数，我求了一下，如果没算错的话，就是100，它说标准差是22.4，那么，有几个人在平均数的一个标准差之下呢？我们就来看看有机个人小于100-22.4，就是有几个人小于77.6.我一看呀，有2个人，那么就选TWO喽，是不是这样子啊？如果对的话留个言哈～

orangerecord

对了啊 我平均数算错了 囧