NO.PZ2015121802000041
问题如下：
A stock with beta of 1.5 is selling for $20 and pay $1 dividend at year end, if the price should be $21 at year end. The stock is undervalued or overvalued? Assuming the risk-free rate is 5%, expected market premium is 5%.
选项：
A.The stock is underpriced, investor should buy it.
B.The sotck is overvalued, investor should short it.
C.The sotck is undervalued, investor should short it.
解释：
B is correct.
Expected return on CAPM = 5 + 1.5 * 5= 12.5%
Estimated return on stock = (21 - 20 + 1) / 20 = 10%
The estimated return is less than expected return on CAPM, indicating that the stock is overvalued, investor should short it.
我之前理解capm模型计算出来的结果是一个预期收益，比如这个数是20%，那代表这支股票预期有20%的收益；
但实际上这支股票只上涨了10%， 那么我会认为，该股还有10%的上涨空间，所以应该继续持有（换句话说就是该股股价被低估了）。
当然从答案我知道这种理解是错的，那么capm正确的理解和用法是什么呢？
