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小伟 · 2020年02月16日

问一道题:NO.PZ2020010801000002

问题如下:

You suspect that the CAPM held on all days except those with a Federal Open Markets Committee (FOMC) announcement, and on these days the β\beta is different. How can a dummy be used to capture this effect? What could you do if you suspected that both a and b are different on FOMC days?

选项:

解释:

The model that allowed differences in the slope would be Ri=α+βRm,i+γIFOMCRm,i+ϵiR_i = \alpha + \beta R_{m,i} + \gamma I_{FOMC} R_{m,i} + \epsilon_i where IFOMCI_{FOMC} is 1 on FOMC days and 0 otherwise. If γ\gamma is not zero, then the slope is different on FOMC days. This can be extended to both parameters by estimating the model

Ri=α+γIFOMC+βRm,i+γIFOMCRm,i+ϵiR_i = \alpha + \gamma I_{FOMC}+\beta R_{m,i} + \gamma I_{FOMC} R_{m,i} + \epsilon_i

请解释下这条题目是怎么理解的

1 个答案

品职答疑小助手雍 · 2020年02月17日

同学你好,题目就是问如果引入哑变量可以测试是否是FOMC日可以导致CAPM回归模型的β和α产生变化。

所以就可以引入哑变量IFOMC,系数是γ,如果是FOMC日,则IFOMC为1,反之为零。

相当于多俩参数参与回归模型,检测这俩参数的系数是否显著为零,为零的话就是是否是FOMC日对CAPM回归起来影响不大,系数不为零的话就是有影响。