FRM Part II · FRM Exam Part II · Beyond Exceedance-Based Backtesting of Value-at-Risk Models
An analyst compares two VaR models using average quantile scores over 500 days and finds Model X has a lower (better) average score than Model Y by a small margin. Before concluding that X is superior, what is the most appropriate next step?
The analyst should test whether the difference in scores is statistically significant, for example with a Diebold-Mariano type test on the daily score differentials. A slightly lower average could be sampling noise, so it does not by itself prove one model is better.
- AApply a statistical test on the score differential, such as a Diebold-Mariano type test, to see if the difference is significantCorrect
- BChoose Model X because any lower average score proves superiority
- CChoose the model with the higher average VaR
- DDiscard both models because scores cannot be compared across models
Explanation
A small difference in average scores may arise from sampling noise. A test on the series of daily score differences, such as Diebold-Mariano, assesses whether the gap is statistically significant. Lower average alone does not establish superiority, and a higher VaR is not inherently better.
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