The most misread number in investing
Win rate feels like the obvious measure of skill, which is exactly why it misleads so many people. A headline like "I hit 60% of my bets" is meaningless without one missing piece: over how many bets? Sixty percent over twenty is well within what pure luck produces; sixty percent over two thousand is a serious signal. The number without the sample is just noise wearing a suit.
Small samples are mostly luck
Over a handful of decisions, randomness dominates completely. A strategy with no edge at all will regularly post great-looking short-term win rates, and a genuinely good strategy will regularly post terrible ones. This is why drawing conclusions from twenty or fifty results is so dangerous: you are reading the weather and calling it the climate.
How confidence grows with sample
As your number of decisions grows, the range of outcomes that pure luck can produce narrows around the true value. With enough decisions, a 55% win rate stops being plausibly explainable by chance and starts being strong evidence of a real edge. You do not need to compute the statistics by hand, but you do need the instinct: trust big samples, distrust small ones, and know roughly where the line sits for your strategy.
Judge strategies on the right timescale
The practical takeaway is to refuse to promote or fire a strategy on a small sample. Decide in advance how many decisions you need before the result means anything, and hold your judgement until you get there. Pair win rate with a forward-looking metric like closing line value, which reaches significance faster, and you stop being whipsawed by every short, noisy streak.