Statistics Formulas Summary
By Dr. Iris Vaughan, Mathematics Editor·Published 20 November 2025·Last reviewed 5 March 2026
Descriptive statistics formulas — mean, median, standard deviation, z-score — plus inference formulas: standard error, confidence interval, test statistics.
Key Formulas
Mean: x̄=Σxᵢ/n
Variance: s²=Σ(xᵢ−x̄)²/(n−1)
z-score: z=(x−μ)/σ
SE: s/√n
95% CI: x̄±1.96·SE (large n)
t-stat: t=(x̄−μ₀)/(s/√n) with df=n−1
Download Printable PDF
Get this cheat sheet formatted for A4 or US Letter printing — no ads, clean layout, exam-ready. $9 via Gumroad.
View in Shop