The plain-English version
Separating examples for fitting a model, choosing its configuration, and assessing the final approach.
Why it matters
It helps distinguish learning useful patterns from adapting repeatedly to the evaluation set.
Let’s make it click
Train on older transactions, tune on a later period, and reserve another period for a final check.
Vibe Bro’s heads-up
Random row splitting can leak information when records from the same person, session, or future period appear on both sides.
The docs behind it
Documentation links checked .
Editorial review · October 28, 2026
Supported: Train/validation/test roles and grouped/time-aware splitting caveats match scikit-learn evaluation guidance.