70 ，75，80，85，90，105，105，130，130，130
The list shown consist of the time, in seconds, that it took each of 10 schoolchridren to run a distance of 400 meters. If the standard deviation of the 10 running time 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 running times.
答案是2个。
这题后面more than 1 standard deviation below the mean of the running times 是什么意思，怎么解出来的啊？请牛人赐教！
9.4/ 9.9/ 9.9/ 9.9/10.1/10.2/10.2/10.5, the mean and standard deviation of the 8 numbers shown are 10.0 and 0.3, respectively. Whant percent of the 8 numbers are within 1 standard deviation of the mean.
为什么有个1 standard deviation. 什么意思？
Is the integer N odd?
1)n is divisible by 3?
2) 2n is divisible by twice as many positive interger as n
答案为什么是B data sufficiency
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