NapkinCalc

Probability — Chance & Counting

What probability means, counting with permutations & combinations, independent events, and the binomial distribution.

Probability is the mathematics of uncertainty — the engine behind insurance, medicine, poker, weather forecasts, and machine learning. Everything below computes live.

  1. 01 What a probability is ELI5: a probability is just a fraction of outcomes that count: P = (favourable outcomes) / (all equally-likely outcomes). It always sits between 0 (impossible)…
  2. 02 Counting — permutations & combinations ELI5: before you can take a fraction of outcomes, you must count them. Permutations = arrangements where order matters (a podium: gold, silver, bronze).…
  3. 03 Independent events & the binomial distribution ELI5: when events don't affect each other (independent), multiply their probabilities — two coin flips both heads is ½ · ½ = ¼. Repeat a yes/no trial n…

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