NO.PZ2021062201000011
问题如下:
A portfolio has an expected mean return of 8% and standard deviation of 14%. The probability that its return falls between 8% and 11% is closest to:
选项:
A.
8.5%
B.
14.8%
C.
58.3%
解释:
A is correct.
P(8%≤ Portfolio return ≤ 11%) = N(Z corresponding to 11%) – N(Z correspondingto 8%).
For the firstterm, NORM.S.DIST(11% – 8%)/14% = 58.48%. To get the second termimmediately, note that 8% is the mean, and for the normal distribution, 50% ofthe probability lies on either side of the mean.
Therefore, N(Z corresponding to 8%) must equal 50%, So, P(8% ≤Portfolio return ≤ 11%) = 0.5848 - 0.50 = 0.0848, or approximately 8.5%.
基于下列总公式:
P(8% ≤ Portfolio return ≤ 11%) = N(Z corresponding to 11%) – N(Z corresponding to 8%).
本公式第一部分:利用excel中NORM.S.DIST这个公式,我们解得:58.48%
本公式第二部分,8%为均值,且为正态分布,则50%的概率落在均值两侧,所以,N(Z corresponding to 8%)=50%,
带入总公式:P(8% ≤ Portfolio return ≤ 11%) = 0.5848 - 0.50 = 0.0848 = 8.5%
老师以后在出这种用到Critical value(不是常见的1,1.65,1.98,和2.58时?) 值的时候,可不可以附上对应的概率呢?