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Roseline · 2020年08月29日

问一道题:NO.PZ2016070202000021

问题如下:

A trading book consists of the following two assets, with correlation of 0.2.

How would the daily VAR at the 99% level change if the bank sells $50 worth of A and buys $50 worth of B? Assume a normal distribution and 250 trading days.

选项:

A.

0.2286

B.

0.4571

C.

0.7705

D.

0.7798

解释:

We compute first the variance of the current portfolio. This is (100×0.25)2+(50×0.20)2+2×0.2(100×0.25)(50×0.20)=825{(100\times0.25)}^2+{(50\times0.20)}^2+2\times0.2{(100\times0.25)}{(50\times0.20)}=825 VAR is then sqrt825×2.33250=4.226sqrt{825}\times\frac{2.33}{\sqrt{250}}=4.226 The new portfolio has positions of $50 and $100, respectively. The variance is  (50×0.25)2+(100×0.20)2+2×0.2(50×0.25)(100×0.20)=656.25{(50\times0.25)}^2+{(100\times0.20)}^2+2\times0.2{(50\times0.25)}{(100\times0.20)}=656.25 VAR is then 3.769 and the difference is -0.457. The new VAR is lower because of the greater weight on asset B, which has lower volatility. Also note that the expected return is irrelevant.

老师好,这道题如果考虑均值,计算过程是否是以下截图步骤?


狂暴小白熊 · 2020年11月11日

工整漂亮

2 个答案
已采纳答案

袁园_品职助教 · 2020年08月30日

是的!

LHY · 2020年10月07日

为什么算expected return的时候不用考虑A和B的权重而直接用100*10%+50*20%呢?

袁园_品职助教 · 2020年10月08日

LHY 同学你好!

权重体现在value上了啊

或者你可以说一下你觉得考虑权重应该怎么算,我们可以继续讨论~