问题如下:
Assume that a random variable follows a normal distribution with a mean of 80 and a standard deviation of 24. What percentage of this distribution is not between 32 and 116?
选项: 4.56%
8.96%
C.13.36%
D.18.15%
解释:
First convert the cutoff points of 32 and 116 into standard normal deviates. The first is , and the second is . From normal tables, P(Z > +1.5) = N(-1.5) = 0.0668 and P(Z < -2.0) = N(-2.0) = 0.0228. Summing gives 8.96%.
这里为什么是P(z>1.5) p(z<-2) 为什么不是p(z<1.5) p(z>-2)