请牛人赐教！

hollycheng

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！

hollycheng

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？

hollycheng

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