Common comparison error
More historical rows do not rescue Overfitting when the sample follows many undisclosed trials or excludes Forward test.
GlossaryStrategy & risk
Overfitting
Designing or selecting rules that match historical noise so closely that they may fail on new data.
Practical use
How to verify Overfitting
Read Overfitting together with Backtest, Forward test, Out-of-sample test. The comparison must preserve the exact rule, value, state, and evidence described below.
A neutral example
A 58% estimate for Overfitting comes from 40 valid outcomes. An interval and larger unseen block replace false precision before comparison with Backtest. The operative detail for Overfitting is concrete: rules tuned to historical noise can collapse when parameters and data are frozen on new observations.
Evidence path
Where to verify Overfitting
Use the source that governs the exact contract, account, entity, or platform state. A general definition cannot replace current broker terms.