Leakage can come from duplicate entities, future events, preprocessing statistics, target-derived features, or contaminated splits. Splitting by the correct unit and time boundary before fitting transformations helps prevent it.
Train-test leakage occurs when information unavailable at real prediction time enters training or development and inflates evaluation results.
Leakage can come from duplicate entities, future events, preprocessing statistics, target-derived features, or contaminated splits. Splitting by the correct unit and time boundary before fitting transformations helps prevent it.