ML Math Lab — K-Fold Cross Validation: The Exam Simulator
Shuffle deck → slice into folds → rotate test fold → get mean + std reliability
Phase: Ready
Hint: press Start
Fold: 0 / 0
Section 1 — What you will learn
✓ By the end you will understand
  • K-Fold: every chunk becomes the exam once.
  • One lucky split can lie: K-Fold checks consistency.
  • Mean accuracy: average score across folds.
  • Std deviation (“fear meter”): high std = unreliable model.
  • Fraud demo: looks good once, fails across folds.
How to learn (step-by-step):
1) Press Single Split → see “lucky” score.
2) Press Start → watch K-Fold rotation & scoring.
3) Use Break it 💥 → noise ↑ → std deviation ↑ (unreliable).
4) Change K & Seed → see consistency change.
Section 2 — Controls
More folds = more exams = better reliability check.
Different models can be stable or unstable across folds.
Change seed to see how luck can fake a single split.
Story helps kids remember what the score means.
Fraud demo = noisy world.

Section 3 — Live stats (Scoreboard)
Fold score (current)
All fold scores
Mean accuracy
Std deviation (fear)
Reliability
Single-split accuracy
Live Chart
Fold accuracy over time

Section 4 — Live math (super simple)
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🧠 Kid Coach
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Tip: low std deviation = reliable model.