我不是伸手党啊
下面附上题和思路 全是我的错题 求大神指正!!!
Soft-drink cans are filled by an automated filling machine. The mean fill volume is 12.1 fluid ounces and the standard deviation is 0.5 fluid ounces. Assume that the fill volumes of the cans are independent, normal random variables.
(a) What is the probability that the average fill volume of 40 cans is below 12 fluid ounces?
(b) How many cans need to be measured such that the probability that the average fill volume is less than 12 fluid ounces is 0.01?
第一题
首先 （12-12.1）/0.5=-0.2'
由normal probability distribution table 得
p(z<=0.2)=0.5793
所以P（z<=-0.2)=1-0.5793=0.4207
所以如果要40罐全部低于12的话就是（0.4207）^40
第二题我是假设（0.4207）^X=0.01 算出来X大约是6
但是交上去这两道题全错了 之前上过一节入门课但是集中在概念方面对计算完全是用一个叫minitab的软件处理的 所以一上课老师就让写就不会了
下面附上题和思路 全是我的错题 求大神指正!!!
Soft-drink cans are filled by an automated filling machine. The mean fill volume is 12.1 fluid ounces and the standard deviation is 0.5 fluid ounces. Assume that the fill volumes of the cans are independent, normal random variables.
(a) What is the probability that the average fill volume of 40 cans is below 12 fluid ounces?
(b) How many cans need to be measured such that the probability that the average fill volume is less than 12 fluid ounces is 0.01?
第一题
首先 （12-12.1）/0.5=-0.2'
由normal probability distribution table 得
p(z<=0.2)=0.5793
所以P（z<=-0.2)=1-0.5793=0.4207
所以如果要40罐全部低于12的话就是（0.4207）^40
第二题我是假设（0.4207）^X=0.01 算出来X大约是6
但是交上去这两道题全错了 之前上过一节入门课但是集中在概念方面对计算完全是用一个叫minitab的软件处理的 所以一上课老师就让写就不会了
