Statistics Guides

Plain-English tutorials that explain the "why" behind the calculators — no jargon, no PhD required.

How to Choose the Right Statistical TestA decision guide + flowchart linking every test to a free calculator. How to Interpret a P-ValueWhat it means, what it doesn't, and why 0.05 is the threshold. Confidence Intervals ExplainedWhy a range of plausible values beats a single p-value. Effect Size ExplainedCohen's d, r, and the difference between significant and important. T-Test vs Z-TestThe one question that decides which you should use. ANOVA vs T-TestWhy you can't just run a t-test on every pair of groups.

Prefer to jump straight to a tool?

All 14 calculators are free and need no sign-up. Start with descriptive statistics, the t-test, or browse the full list on the homepage.