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Answer: We will probably call the model bad (inaccurate) but we risk a Type I error.
## Explanation ### Key Information: - **Confidence Level**: 99% VaR - **Number of Observations**: 1,000 - **Observed Exceptions**: 25 - **Null Hypothesis (H₀)**: VaR model is accurate - **Expected Exceptions**: At 99% confidence level, we expect 1% exceptions = 10 exceptions out of 1,000 observations ### Analysis: 1. **Expected vs. Actual Exceptions**: - Expected: 10 exceptions (1% of 1,000) - Actual: 25 exceptions - The actual exceptions (25) are significantly higher than expected (10) 2. **Statistical Testing**: - With 25 exceptions vs. expected 10, this is statistically significant - We would likely **reject the null hypothesis** that the VaR model is accurate - Therefore, we would probably call the model **bad (inaccurate)** 3. **Type I vs. Type II Error**: - **Type I Error (False Positive)**: Rejecting a true null hypothesis - Risk: We might reject an actually accurate model - **Type II Error (False Negative)**: Failing to reject a false null hypothesis - Risk: We might accept an actually inaccurate model 4. **Conclusion**: - Since we're rejecting H₀ (model is accurate), we risk making a **Type I error** - We might be rejecting an actually good model - This corresponds to **Option C**: "We will probably call the model bad (inaccurate) but we risk a Type I error" ### Basel II Backtesting Framework: The Basel Committee uses a traffic light approach where: - **Green Zone**: 0-4 exceptions (model acceptable) - **Yellow Zone**: 5-9 exceptions (model may need improvement) - **Red Zone**: 10+ exceptions (model likely inadequate) With 25 exceptions, the model is clearly in the red zone and would be considered inadequate.
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Basel II requires a backtest at a 99% confidence level of a bank's internal value at risk (VaR) model (IMA). Assume the bank's ten-day 99% VaR is $1 million (minimum of 99% is hard-wired per Basel). The null hypothesis is: the VaR model is accurate. Out of 1,000 observations, 25 exceptions are observed (we saw the actual loss exceed the VaR 25 out of 1000 observations).
A
We will probably call the VaR model good (accurate) but we risk a Type I error.
B
We will probably call the VaR model good (accurate) but we risk a Type II error.
C
We will probably call the model bad (inaccurate) but we risk a Type I error.
D
We will probably call the model bad (inaccurate) but we risk a Type II error.