YL2023-01-06 21:05:37

教材P259-（1）第2问，请问用公式怎么表示？What is the probability that returns would be between +1 and -1 standard deviation around the mean? 用公式怎么表示？ 这句话和P259 Solution to 2中从第3行开始的the difference between the cdf one standard deviation above the mean and the cdf one standard deviation below the mean. 是同一个含义吗？（2）另外，教材P259-Solution to 2中第8行，为什么是fall below the mean plus one standard deviation, 而不是above the mean plus one stadard deviation? （3）Solution to 2答案的最后一句话不太好理解？为什么要在84.1%的基础上再减去15.9%？不太能够理解<=1 standard deviation below the mean与between +1 and -1 standard deviation around the mean，之间的关系。