quant-backtesting-info



The Quant's Gauntlet: A Visual Guide to Backtesting

The Quant's Gauntlet

Why most trading strategies fail, and how to build one that works. A visual guide to rigorous backtesting.

The 7 Deadly Sins of Backtesting

A flawed backtest is a factory for false hope. These common biases create the illusion of profitability where none exists. Avoiding them is the first and most critical step.

😈

Overfitting

Mistaking historical noise for a real signal. The strategy perfectly "memorizes" the past but fails in the future.

🔮

Look-Ahead Bias

Using information in the simulation that would not have been available at the time of the trade decision.

👻

Survivorship Bias

Testing only on stocks that "survived," ignoring the bankrupt companies where the strategy would have failed.

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Ignoring Costs

Forgetting that commissions and slippage can turn a "profitable" high-frequency strategy into a losing one.

The Validation Gauntlet

Financial data is not random. Standard validation methods create "data leakage," leading to unrealistically smooth equity curves. A Walk-Forward Analysis (WFA) respects the timeline, revealing a more honest, and often harsher, reality.

Illustrative equity curves. The flawed backtest shows dangerously optimistic results due to data leakage.

The Bet Sizing Crucible

A good signal is useless without smart risk management. Bet sizing determines how much capital to risk per trade. As the chart shows, this single choice has a profound impact on growth, volatility, and the risk of ruin.

Illustrative curves. Full Kelly maximizes growth but with extreme volatility. Fixed Fractional is conservative. Half Kelly offers a balance.

The Final Judgement: Performance Dashboard

Total return is a vanity metric. A robust strategy is judged by its risk-adjusted performance. These key metrics provide a holistic view of a strategy's true character.

Sharpe Ratio

1.25

Return per unit of risk

Max Drawdown

-22%

Worst peak-to-trough loss

Calmar Ratio

0.95

Return vs. drawdown

Profit Factor

1.80

Gross wins / Gross losses

The Quant's Process: From Idea to Execution

Data Integrity

Source high-quality, point-in-time data that includes delisted assets to eliminate survivorship and look-ahead bias.

Rigorous Validation

Use Walk-Forward Analysis or Purged CV. Never use standard K-Fold CV on time-series data. This is the primary defense against overfitting.

Smart Bet Sizing

Implement a formal risk management model like Fixed Fractional or Fractional Kelly. A signal is not a strategy without bet sizing.

Execution Simulation

Model realistic transaction costs. A backtest that ignores commissions and slippage is a fantasy.

Holistic Evaluation

Analyze a full suite of performance metrics. Look beyond total return to understand the true risk-adjusted character of the strategy.

Content synthesized from "Rigorous Backtesting of Machine Learning Strategies in Finance." For educational purposes only.




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