Glossary
Out-of-sample
Testing a strategy on data it was never tuned on. A rule that looks great on the data used to build it (in-sample) often collapses out-of-sample — the honest test of whether an edge is real.
In plain terms
The usual recipe is a hard split: tune every knob on one period (in-sample), freeze the rule, then run it once on a later period it has never seen. Re-running the out-of-sample test many times and keeping the best result quietly turns it back into an in-sample test.
Every headline result on this site is out-of-sample by that strict recipe. It is the single biggest reason our numbers look worse — and more honest — than typical backtest marketing.
Related terms
Educational definitions only. Not investment advice.