Coin-Flip Streak Lab
After five heads in a row, is tails “due”? Flip ten thousand coins and measure it. Then try to fake 100 random flips — most people can't.
Flip the coin.
Running share of heads
The line wobbles early, then settles toward 50% — the law of large numbers in action.
Can you fake randomness?
Click H or T 100 times as “randomly” as you can (or type a sequence). We'll compare it with a real coin.
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Streaks are normal. “Due” is not.
A fair coin has no memory, so the chance of heads on the next flip is 50% no matter what came before. Yet long streaks are far more common than intuition expects: in 100 flips a run of six or more identical results is the usual outcome, not a rare one. Gamblers who see such a run often conclude the other side is “due” — the gambler's fallacy.
Human-made sequences give themselves away: they switch sides too often and avoid long runs. A real coin switches about half the time and produces streaks that look “suspicious”. Roulette wheels and dice behave the same way — see the Roulette Simulator.