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A bank's model validation team is in the process of conducting a backtest of the institution's Value at Risk (VaR) model. As they prepare for the backtest, a team member expresses concern about the possibility of committing either a Type I error or a Type II error during the validation process. The team member then outlines the characteristics of these errors for the group. Can you explain the proper understanding of Type I and Type II errors in this context?
Explanation:
The correct answer is A. The probability of committing a Type II error decreases when the sample size increases and the level of significance is held constant. This is because as the sample size grows, the confidence interval around the estimate of the model's performance becomes narrower, making it easier to detect if the model is incorrectly specified.
Option B is incorrect because a test is considered statistically powerful if it minimizes the probability of committing both Type I and Type II errors, not just Type II.
Option C is incorrect because a Type I error occurs when a correctly specified model is incorrectly rejected.
Option D is incorrect because a Type II error occurs when an incorrectly specified model is not rejected.
In summary, Type I error is the incorrect rejection of a true null hypothesis, while Type II error is the failure to reject a false null hypothesis. The balance between these errors is crucial in model validation and backtesting to ensure accurate risk assessment and management.