A coin toss is supposed to be the fairest way to settle a dispute. A marathon experiment involving 350,757 flips found that it is very slightly tilted, not by the coin, but by the person flipping it.
Coins landed on the same side they started on 50.8% of the time, according to the study, which won the 2024 Ig Nobel Prize in Probability and was published after peer review in the Journal of the American Statistical Association in 2025. The bigger surprise was how much the effect varied from person to person, and how it seemed to fade with practice.
