标题: prep 数学请教！！ [打印本页] 作者: y0608x 时间: 2010-2-9 15:11 标题: prep 数学请教！！ 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 starndard deviation of the 10 running times is 22.4 seconds, rounded to the nearest tenth of a second, how many of 10 running times are more than 1 starndard deviation below the mean of the 10 running times? A.1 B.2 C.4 D.5 E.6 答案是B 我想问下这题什么意思？？作者: y0608x 时间: 2010-2-9 22:45
大家帮帮忙~~ 后天要考试了...作者: tibet 时间: 2010-2-9 23:06
你可真行 list都不给作者: y0608x 时间: 2010-2-9 23:23
晕~ 怪不得没人理我 list 是70 75 80 85 90 105 105 130 130 130作者: tibet 时间: 2010-2-9 23:32
求出平均值mean mean减去1个standard deviation 比那个值小的数据个数就是了作者: y0608x 时间: 2010-2-9 23:36
原来是这个意思~~ 感谢感谢~~~