Read the world in data,
one belt at a time.
Statistics is the art of telling signal from noise — and it's taught badly almost everywhere. Stat Dojo teaches it the way Freedman, Pisani & Purves do: with pictures and plain reasoning, not calculus. Summarize data with an average and an SD, put a number on chance, watch a bell curve appear out of nowhere, fit a line through a cloud of points — then make the leap every scientist makes, from a single sample to a claim about the whole world.
Before you can reason about data you have to see it. Learn to read a histogram, find the center of a batch of numbers with the average and the median, and measure its spread with the standard deviation — the three numbers that summarize almost any dataset.
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Level 1 · ▶ NEXT Variables & Distributions ★★★ ◆
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Level 2 Histograms & the Density Scale ★★★ ◆ 🧩 Builds on L01
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Level 3 The Average & the Median ★★★ ◆ 🧩 Builds on L02
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Level 4 The Standard Deviation ★★★ ◆◆ 🧩 Builds on L03
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👑Level 5 · EXAM Describing Data Exam ★★★ ◆◆ 🧩 Builds on L04
Chance is a number between 0 and 1, and it obeys just two rules — add for 'or', multiply for 'and'. Build probability from the ground up, learn where independence breaks down, and meet the box model: the single picture Freedman uses to reason about every game of chance.
The same bell-shaped curve turns up everywhere — test scores, heights, measurement errors, chance sums. Learn to convert any value to standard units, read areas off the normal curve, and use the 68-95-99.7 rule to answer 'how unusual is this?' at a glance.
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Level 11 Standard Units ★★★ ◆◆ 🧩 Builds on L10
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Level 12 The Normal Curve & the 68-95-99.7 Rule ★★★ ◆◆ 🧩 Builds on L11
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Level 13 Percentiles & the Normal Table ★★★ ◆◆◆ 🧩 Builds on L12
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Level 14 The Normal Approximation for Chances ★★★ ◆◆◆ 🧩 Builds on L13
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👑Level 15 · EXAM Normal Curve Exam ★★★ ◆◆◆ 🧩 Builds on L14
When two things vary together, how do you measure it — and how do you predict one from the other? Read scatter diagrams, put a number on association with the correlation coefficient, fit the regression line, and learn the traps: outliers, the regression effect, and why correlation is not causation.
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Level 16 Scatter Diagrams & Association ★★★ ◆◆ 🧩 Builds on L15
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Level 17 The Correlation Coefficient ★★★ ◆◆◆ 🧩 Builds on L16
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Level 18 The Regression Line ★★★ ◆◆◆ 🧩 Builds on L17
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Level 19 Prediction & RMS Error ★★★ ◆◆◆ 🧩 Builds on L18
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👑Level 20 · EXAM Correlation & Regression Exam ★★★ ◆◆◆ 🧩 Builds on L19
This is the whole point. A sample is small and random, the truth is large and fixed — how do you cross the gap? Meet the central limit theorem and the standard error, build confidence intervals, run tests of significance, and finish with the chi-square test. Earn your black belt.
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Level 21 Samples, Populations & Bias ★★★ ◆◆ 🧩 Builds on L20
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Level 22 The Central Limit Theorem & Standard Error ★★★ ◆◆◆ 🧩 Builds on L21
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Level 23 Confidence Intervals ★★★ ◆◆◆ 🧩 Builds on L22
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Level 24 Tests of Significance ★★★ ◆◆◆◆ 🧩 Builds on L23
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Level 25 The Chi-Square Test ★★★ ◆◆◆◆ 🧩 Builds on L24
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👑Level 26 · EXAM The Black Belt Exam ★★★ ◆◆◆◆ 🧩 Builds on L25
Earn your Stat Dojo black belt
Clear all 26 levels and the five exams to walk away with a working feel for statistics: how to describe data honestly, reason about chance, use the normal curve, read a scatter and a regression line — and, above all, how a confidence interval and a test of significance turn a noisy sample into a defensible conclusion. This is the literacy behind every study, poll, and headline you'll ever read.
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