怎么查表呢

NO.PZ2017092702000087 问题如下 A portfolio hexpectemereturn of 8 percent anstanrviation of 14 percent. The probability thits return falls between 8 an11 percent is closest to: A.8.3% B.14.8%. C.58.3%. A is correct. P(8% ≤ Portfolio return ≤ 11%) = N(Z corresponng to 11%) - N(Z corresponng to 8%). For the first term, Z = (11% – 8%)/14% = 0.21 approximately, anusing the table of cumulative normstribution given in the problem, N(0.21) = 0.5832. To get the seconterm immeately, note th8 percent is the mean, anfor the normstribution 50 percent of the probability lies on either si of the mean. Therefore, N(Z corresponng to 8%) must equ50 percent. So P(8% ≤ Portfolio return ≤ 11%) = 0.5832 – 0.50 = 0.0832 or approximately 8.3 percent. 1.（11%-8%）/14%是对正态分布标准化的过程，直接套用标注化公式（X-均值）/标准差， 即可。2. 标准化后得到的关键值就是Z值，之后可以通过查表求得对应的概率。比如N(0.5832)3. 题目要求的P(8%＜X＜11%)，我们可以求得P(X＜11%)以及P(X＜8%)，再用前者减去后者 这是MOLE4 基础视频里第几个视频有知识点讲解?我重新看一遍，谢谢。

我看题干没有说portfolio符合正态分布？

14.8%. 58.3%. A is correct. P(8% ≤ Portfolio return ≤ 11%) = N(Z corresponng to 11%) – N(Z corresponng to 8%). For the first term, Z = (11% – 8%)/14% = 0.21 approximately, anusing the table of cumulative normstribution given in the problem, N(0.21) = 0.5832. To get the seconterm immeately, note th8 percent is the mean, anfor the normstribution 50 percent of the probability lies on either si of the mean. Therefore, N(Z corresponng to 8%) must equ50 percent. So P(8% ≤ Portfolio return ≤ 11%) = 0.5832 – 0.50 = 0.0832 or approximately 8.3 percent.老师， 请问一下 x≦8的概率具体求法不是应该也标准化吗？那x-8/14应该等于零啊？答案的50％怎样用公式算呢？

这个是啥知识点，以及门将讲解一下这么算的原因吗