65-Day Academy · Day 27 · Technical Analysis
Overfitting Indicators — the Backtest Mirage
The curve-fitting trap
Given enough parameters (periods, thresholds, filters), ANY indicator system can be tuned to fit past data perfectly — and fail instantly forward. If your RSI works at 14 but not 13 or 15, you have fit noise, not signal. Robust rules are FLAT around their parameters: 14 works, and so do 12–16.
The honest backtest checklist
Out-of-sample testing (tune on 2015–2019, verify on 2020–2024), realistic costs (spread + slippage + the fills you will actually get), survivorship-free data, and a parameter-sensitivity check. A strategy that survives all four is rare — and that rarity is the point: most published "systems" die at step one.
What you'll practise
Which practices protect against indicator overfitting? (Select all that apply)
10 XP in the app · introductory
Sources
- Overfitting in Trading SystemsInvestopedia
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All lessons are for educational purposes only and are not individualized financial advice, a recommendation, or a solicitation to buy or sell any security. Options involve substantial risk and are not suitable for every investor.