Training, Validation & Model Selection

Cross-Validation Playground

Watch validation folds move through the dataset and compare both average performance and variability.

Lab concept guide

What to observe while you experiment

Cross-validation estimates how a modelling workflow behaves across multiple train/validation partitions. The fold geometry matters: ordinary K-Fold, stratification, groups and time-aware splitting encode different assumptions about which observations may be separated.

MechanismInspect which observations enter training and validation in each fold, then connect each fold score to that exact split.
Failure modeAveraging fold scores while ignoring forbidden group/time overlap or performing preprocessing once before the folds.
VerificationCheck fold indices directly, confirm no prohibited overlap, and recompute the reported mean/variability from the individual fold scores.
Experiment deliberately
Run all folds, then change the split method while keeping the dataset/model fixed. Predict how class balance or dependency leakage should change.
Validation is a sampling procedure. Use the fold visualiser to inspect which observations are training vs validation in each iteration, then compare fold-to-fold variability.
Ready.

Fold map

Reset prepares the folds. Run next fold generates one model/result at a time; completed folds become available for inspection.

Current fold geometry with model

Fold scores