## 9.7 Resampling methods (6): k-Fold Cross-Validation

• James et al. (2013) use Figure 5.5 [p.179] to explain the k-Fold Cross-Validation. Please inspect the figure and explain it in a few words.

• k-Fold Cross-Validation is special case of LOOCV where $$k$$ is set to equal $$n$$

• Error rate: $$CV_{(k)} = \frac{1}{k}\sum_{i=1}^{k}Err_{i}$$

• Q: What is the advantage of using $$k = 5$$ or $$k = 10$$ rather than $$k = n$$? [computation!]