#loocv

Question 1: Single choice

The figure shows two cross-validation schemes on a data set of 10 examples. Each row is one training run, and the dark cells are the examples held out for validation in that run. What are the schemes, and how many models does each one fit?

Two grids of 10 columns, numbered 1 to 10. Scheme 1 has 10 rows, and row i has only cell i dark. Scheme 2 has 5 rows, and row k has the two cells 2k−1 and 2k dark. Dark means validation, light means training.

Scheme 1 is leave-one-out (10 models), scheme 2 is 5-fold (5 models)1
Scheme 1 is 10-fold and scheme 2 is 5-fold, each refitting one model2
Scheme 1 is leave-one-out (1 model), scheme 2 is 2-fold (5 models)3
Scheme 1 is a bootstrap (10 models), scheme 2 is stratified (5 models)4

Timed test