Predictable Randomness

When chance becomes certainty

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• For $n$ coin flips: mean $n/2$, standard deviation $\sqrt n / 2$.
• The fraction of successes settles down (law of large numbers).
• Large samples make even small biases detectable.

Steps

1. Spread grows slower than the mean
2. A thousand flips
3. Catching a slightly biased coin
4. The house always wins
5. Ten thousand flips
6. Suspicious coin