Parameter sensitivity

How much a strategy’s performance changes as a parameter is nudged. A robust system changes smoothly; if a tiny change to a lookback flips the result from great to terrible, you have found a fragile peak rather than a genuine edge. Widely divergent optimized parameters between walk-forward windows are a curve-fit tell.

First used in Lesson 2.7 · Walk-forward: the honest way to test an optimized system — the lesson that makes this term real.