Chance Didn’t Have to Be This Hard · Chapter 4

Two-Way Table

“Given” means shrink your world to one group and count inside it. The chance of A given B is not the chance of B given A, and a table shows both.

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From the book, Chapter 4. The book’s 1,000 commutes: 300 rainy, 120 of them late; 70 of the 700 dry ones late. Late overall 19%; late given rain 40%; late given dry 10%; but rain given late is 63.2%. The lucky shirt won 60% of games with it and 60% without: independent.

Exact arithmetic, worked the way the book shows. Everything stays in your browser: no sign-up, nothing stored or sent.