Solution: Manual Three-Fold Cross-Validation

Exercise: Manual Three-Fold Cross-Validation

Solution

Three models are fit. Each model trains on 8 observations and validates on 4. Every observation is held out exactly once.

Takeaways

• State the assumption that makes the method valid before trusting the result.
• Connect the computation back to the finance workflow, not only to the code.
• Check whether the result depends on average-case behaviour, validation design, or numerical safeguards.