STATISTICS,急求解答方法,Supposethat175outofasampleof625testtubesshowedwaterpollution.LetXbearandomvariablewhichtakesthevalues0foranon-pollutedtesttubeand1forapollutedtesttube.Determinethesamplemean,medianan

Question

STATISTICS,急求解答方法,
Suppose that 175 out of a sample of 625 test tubes showed water pollution.Let X be a random variable which takes the values 0 for a non-polluted test tube and 1for a polluted test tube.Determine the sample mean,median and standard deviation

Answer 1

625试管中,共有175显示水污染.如让未知数X的值来代表样品,当试管是污染的时候,X = 0, 纯净的时候 X = 1. 计算X值的平均,中位数和标准差.
从题中可知数列中有 175个“0”, 450个“1”. 平均计算为 (450 + 0)/625 = 18/25 = 0.72
中位数计算是把全部的数从小到大排列,然后取中间的数,这个数列中有奇数个值,所以不用做平均,X = 1 的数量明显比 X = 0 多,所以MEDIAN为“1”.
标准差公式我忘了,楼主可以查一查.在EXCEL里面可以做 F(X) = STDEV, 或用图形计算器算.