题目
The return on a portfolio is normally distributed with an expected rate of return of 10%, and a standard deviation of 20%. What is the probability that the return will be between 0% and 5%?
选项
A.7%
B.9%
C.11%
D.13%
答案
B
解析
With a mean 10% and standard deviation of 20%, the value of 0% would be (0% - 10%)/20% or -0.5 standard deviation from the mean, and the value of 5% would be (5% - 10%)/20%or -0.25 standard deviations from the mean. By referring to the distribution tables, we can ascertain how much of the distribution lies under these points. The area between the mean and 5% is 0.0987, and 0.1915 between the mean and 0%. The difference of 0.0928(approximately 9%) is the value of the distribution which lies between 0% and 5%. 如果平均值为10％，标准偏差为20％，则0％的值将为平均值的（0％-10％）/ 20％或-0.5标准偏差，而5％的值将为（5％- 平均值的10％）/ 20％或-0.25标准偏差。 通过参考分布表，我们可以确定在这些点下有多少分布。 平均值与5％之间的区域为0.0987，平均值与0％之间的区域为0.1915。 差异值0.0928（约9％）是分布值，介于0％和5％之间。