PART E โ KEY FORMULAS & CONCEPTS CHEAT SHEET
Statisticsโ
| Concept | Formula |
|---|---|
| Mean | ฮผ = ฮฃxแตข / N |
| Variance | ฯยฒ = ฮฃ(xแตข - ฮผ)ยฒ / N |
| Standard Deviation | ฯ = โ(Variance) |
| Pearson Correlation | r = Cov(X,Y) / (ฯโ ร ฯแตง) |
| Z-score | z = (x - ฮผ) / ฯ |
| Confidence Interval (95%) | xฬ ยฑ 1.96 ร (ฯ / โn) |
ML Evaluation Metricsโ
| Metric | Formula | When to Use |
|---|---|---|
| Accuracy | (TP+TN) / Total | Balanced classes only |
| Precision | TP / (TP+FP) | When false positives are costly (spam detection) |
| Recall | TP / (TP+FN) | When false negatives are costly (churn, disease) |
| F1-Score | 2 ร (PรR) / (P+R) | Balance between precision and recall |
| AUC-ROC | Area under ROC curve | Overall model discrimination ability |
| MAPE | Mean( | Actual-Predicted |