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cenwandada · 2024年07月25日

感觉4个选择都对吧。

NO.PZ2023100703000038

问题如下:

You are backtesting a bank’s VaR model. Currently, the bank calculates a 1-day VaR at the 99% confidence level, and you are recommending that is switch to a 95% confidence level. Which of the following statements concerning this switch is correct?

选项:

A.The 95% VaR model is less likely to be rejected using backtesting than the 99% VaR model.

B.When validating with backtesting at the 90% confidence level, there is a smaller probability of incorrectly rejecting a 95% VaR model when it is valid than a 99% VaR model.

C.The decision to accept or reject a VaR model based on backtesting results is more reliable with a 95% confidence level VaR model than with a 99% confidence level model.

D.When backtesting using a 90% confidence level, there is a smaller probability of committing a type I error when backtesting a 95% VaR model than with a 99% VaR model.

解释:

The concept tested here is the understanding of the difference between the VaR parameter for confidence (here, namely 95% vs 99%) and the validation procedure confidence level, and how they interact with one another. Using a VaR confidence level creates a narrower rejection region by allowing a greater number of exceptions to be generated. This in turn increases the power of the backtesting process and makes for a more reliable test.

感觉4个选择都对吧。

3 个答案

pzqa27 · 2024年09月18日

嗨,从没放弃的小努力你好:


B回测拒绝域是10%,为什么95%和99%var是一样概率?

因为题目说了,回测的置信区间是90%,也就是这个回测有10%的概率去拒绝原假设,所以不论是哪种VaR,它们被拒绝的概率是一样的。


回测拒绝域和var拒绝域是同一个概念吗

回测的置信区间和VaR的置信区间是2个东西,回测是在做假设检验,而VaR的概率指的是分位点。这里讨论的是拒绝概率,不是分位点,所以不论是95%的VaR还是90%的VaR,它们的拒绝概率是一样的。

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虽然现在很辛苦,但努力过的感觉真的很好,加油!

pzqa27 · 2024年07月25日

嗨,爱思考的PZer你好:


不是,题目只说了对比95%VaR和99% VaR的回测情况,只要它们回测的置信区间是一样的,那么这2种VaR的被意外拒绝的概率是一样的。

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就算太阳没有迎着我们而来,我们正在朝着它而去,加油!

pzqa27 · 2024年07月25日

嗨,爱思考的PZer你好:


不是,只有C是对的,其他都是错的。

A说95%VaR和99%VaR对比,95% VaR更不容易被回测拒绝。这个不对回测的confidence level都是95%,因此它们俩被拒绝的概率是一样的。

B说如果把回测的confidence level改成90%,拒真的概率在95%的VaR比99%VaR要低,拒真的概率是1类错误的概率,它就是回测的拒绝域的概率,就是1-90%=10%, 因此95%的VaR和99%VaR是一样的。D选项跟B说的是一个意思,所以B错了D肯定也错了。

C是对的,没有什么问题,这里就不展开了。


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加油吧,让我们一起遇见更好的自己!

cenwandada · 2024年07月25日

这题目只说了var置信区间,回测置信度没提吧。相比99%,95%不容易被意外数据拒绝吧。

C_M_ · 2024年09月14日

B回测拒绝域是10%,为什么95%和99%var是一样概率?回测拒绝域和var拒绝域是同一个概念吗

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