Essay
What a Backtest Cannot Tell You
- Published
- 12 OCT 2026
- Reading
- 1 MIN
- Status
- DEMONSTRATION ENTRY
A backtest is a description of the past under a set of assumptions. It is evidence, not a forecast.
DEMONSTRATION ESSAY — placeholder prose to show the reading experience.
A backtest answers a narrow question: given these rules and this data, what would have happened? It does not answer whether the rules will continue to work.
Three things worth separating
Description. The numbers are exact for the sample.
Inference. What the sample suggests about the process that generated it — this is where uncertainty lives.
Decision. What to do under that uncertainty, including how much to risk.
A working habit
Write the hypothesis before running the test. Record every variation. Prefer the simpler explanation.