FRM Part II · FRM Exam Part II · Case Study: Model Risk and Model Validation
Validators find that a bank's loan loss model was tuned so closely to the development sample that it fits historical noise and performs poorly on out-of-sample data. This is best described as which type of model risk?
This is overfitting: the model captures noise specific to the development sample, giving strong in-sample fit but poor out-of-sample predictions. It is a model construction weakness, detectable through out-of-sample testing, not a problem of scope, documentation, or aggregation.
- AOverfitting leading to poor generalizationCorrect
- BModel use outside its scope
- CStale documentation
- DAggregation of model outputs across business lines
Explanation
Overfitting occurs when a model captures random noise specific to the development sample, so in-sample fit is strong but out-of-sample performance is weak. It is a model construction weakness, detected by out-of-sample testing, rather than a use or documentation problem.
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