4. DRIFT DETECTION (CUSUM ALGORITHM)
Detects sustained performance changes, not daily noise.
CUSUM ALGORITHM:
For each new score:
1. Compare to baseline (historical average)
2. Calculate deviation: δ = new_score - baseline
3. Update CUSUM: S = max(0, S + δ - k)
4. If S > threshold: ALERT (drift detected)
Parameters:
• Baseline window: 12 runs
• Sensitivity (k): 0.005
• Threshold (λ): 0.5
• False positive rate: <2%
ALERT SEVERITY LEVELS:
🟢 NORMAL - Performance within expected variance
🟡 WARNING - Slight decline, monitoring closely
🟠 DEGRADATION - Sustained decline confirmed
🔴 CRITICAL - Major drop, immediate attention needed