问题
单项选择题
There is a 30% chance that the economy will be good and a 70% chance that it will be bad. If the economy is good, your returns will be 20% and if the economy is bad, your returns will be 10%. What is your expected return（）
A. 15%.
B. 17%.
C. 13%.
答案
参考答案：C
解析：
Expected value is the probability weighted average of the possible outcomes of the random variable. The expected return is: ((0.3)× (0.2))+((0.7)×(0.1))=(0.06)+(0.07)=0.13=13%.