| x̄ = Σx / n | Sample mean |
| s² = Σ(xᵢ − x̄)² / (n−1) | Sample variance (Bessel's correction) |
| IQR = Q3 − Q1 | Interquartile range; outlier if beyond 1.5×IQR |
| z = (x − μ) / σ | Standardized score (z-score) |
| P(A ∪ B) = P(A)+P(B)−P(A∩B) | Addition rule (general) |
| P(A|B) = P(A∩B)/P(B) | Conditional probability |
| μₓ = np ; σₓ = √(np(1−p)) | Binomial mean & SD |
| σ(x̄) = σ/√n | Standard error of sample mean |
| σ(p̂) = √(p(1−p)/n) | Standard error of sample proportion |
| t = (x̄ − μ₀) / (s/√n) | One-sample t-test statistic |
| z = (p̂ − p₀) / √(p₀(1−p₀)/n) | One-proportion z-test |
| CI: x̄ ± t* · (s/√n) | Confidence interval for μ |
| r = Σ[(xᵢ−x̄)/sₓ][(yᵢ−ȳ)/sᵧ] / (n−1) | Pearson correlation coefficient |
| ŷ = b₀ + b₁x ; b₁ = r(sᵧ/sₓ) | Least-squares regression |
| χ² = Σ(O−E)²/E | Chi-square test statistic |