问题
单项选择题
The following shows the yearly returns of aggressive equity funds for four years: 1999=+5% 2000=+2% 2001=+1% 2002=-4% Assume that this distribution can represent either the population or a sample of aggressive equity funds. Calculate the population and sample standard deviation. Population Standard DeviationSample Standard Deviation（）
A. 2.73% 3.99%
B. 3.09% 4.55%
C. 3.24% 3.74%
答案
参考答案：C
解析：
Step 1. Calculate the mean monthly return =2%+(-4%)+1%+5%=4%, M=1%.
Step 2. Calculate the population standard deviation: ([(2%-1%)2+(-4%-1%)2+(1%-1%)2+(5% -1%)2])(1/N)2=3.24%.
Step 3. Calculate the sample standard deviation: ([(2%-1%)2+(-4%-1% )2+(1%-1%)2+(5%-1%)2])/(n-1)2=3.74%.