The free course
The Backtest Trap
Every strategy looks brilliant in a backtest — that is what backtests are for. This course teaches the difference between testing a system and flattering one: the biases that fake an edge, why small samples lie, and the honest protocol that survives contact with the future. Unusually, every mistake in it is illustrated from our own published research — because we made most of them in public.
6 min01
The Seductive Curve
A backtest is not evidence that a strategy works. It is evidence that a strategy can be made to have worked.
7 min02The Five Ways a Test Lies
Overfitting is only the most famous liar in the room. Four quieter ones corrupt tests that were never even tuned.
6 min03Twenty Trades Prove Nothing
The most common backtest error isn't a bias at all. It's believing a number that hasn't earned belief yet.
6 min04Choose Plateaus, Not Peaks
When a parameter sweep crowns a winner, the winner is usually the luckiest cell in the spreadsheet — not the best rule.
7 min05Pre-Registration: The Honest Protocol
Science solved this exact problem decades ago. The solution transfers to trading completely — and almost nobody uses it.