Parameter Sensitivity Analysis

A strategy optimized to Sharpe 2.0 at lookback=21 that drops to 0.3 at lookback=20 or lookback=22 is not a strategy - it is a curve fit. Sensitivity analysis sweeps parameters to verify that performance is stable across a neighborhood, not balanced on a knife edge.

The Problem

Single-parameter backtests find the best setting. But the best setting may be a statistical fluke - one data point away from failure. If small perturbations in entry threshold, lookback period, or position sizing cause large performance swings, the parameters are overfit. You need to see the performance surface, not just its peak.

The Pattern

WRONG

import numpy as np