Mathematics · advanced
Momentum Backtest Discipline
Momentum rules, SPY/QQQ benchmarks, holdout honesty — why most backtests lie.
Mental model
Backtest = hypothesis on history. Pre-register rule, holdout/walk-forward, benchmark, document costs. In-sample-only edge is curve-fit.
How to study Momentum Backtest Discipline
Begin by restating the mental model in your own words, then connect it to a concrete system you have built or operated. Name the mechanism, the constraint it addresses, and the trade-off it introduces. Use QuantConnect — Backtesting overview to check details, but close the source before writing your explanation. Retrieval is the learning step; rereading is only preparation.
Next, compare Momentum Backtest Discipline with A/B Testing for Engineers, Stationarity & Autocorrelation. Ask what changes in correctness, latency, resource use, operability, and failure recovery. Complete Design an honest momentum backtest and preserve the command, input, output, and one failed attempt as evidence. Finish by explaining the idea without jargon to someone who has not studied the track.
Proof of understanding
- Explain the mechanism from first principles and identify the state it reads or changes.
- Give one situation where the concept is the right choice and one where it is not.
- Predict a realistic failure mode before running the drill, then compare the prediction with evidence.
- Connect the result to a roadmap or build artifact instead of treating the concept as isolated trivia.
Where it matters
Quant research prototyping, BS detection.
Common mistakes
- Optimizing lookback on full history
- Survivorship bias
- No benchmark
Learn from primary sources
Practice and explain it back
Design an honest momentum backtest
Outline a 12-month momentum rule on 3 ETFs: train/holdout split, benchmark (SPY), transaction cost assumption, metrics (CAGR, Sharpe, max DD), and three ways your backtest could lie to you.
Expected evidence: Written protocol before code; explicit holdout; limitations section mandatory.
Open the interactive drill →Review prompts
- Why do most backtests overfit?
Build evidence
Simple momentum backtest vs SPY/QQQ
12-month momentum rule on 1–3 names; compare cumulative return to SPY or QQQ over the same window. State assumptions and survivorship bias.
- Rule written before seeing full-sample results (or use holdout half)
- Equity curve: strategy vs benchmark
- Honest limitations section (costs, slippage, overfitting)