Honest Trading Research

The 10 Biases That Destroy Your Backtest

Every trading backtest you've ever seen is probably lying. Not because someone is evil, but because at least one of ten invisible biases is hiding in the numbers. Here's how to spot them — and one strategy that survived all ten.

The 10 Deadliest Biases in Trading Backtests
⭐ Pillar Article
Start Here

The 10 Deadliest Biases in Trading Backtests

How I lost $12M on paper with my sister's strategy — and found real alpha instead.

Read the full pillar15 min read

Deep Dives — One Per Bias

16 published
Data-Snooping: 3.2 Million Parameter Combinations. Your "Winner" Is Noise.
Trading Bias6 min

Data-Snooping: 3.2 Million Parameter Combinations. Your "Winner" Is Noise.

Test every combo. Find the best one. Call it a discovery. Statistics says 80 percent of the time, you're lying to yourself.

Apr 16, 2026
DT
Dominic
Recency Bias: Why Last Year's Winners Usually Lose Next Year
Trading Bias5 min

Recency Bias: Why Last Year's Winners Usually Lose Next Year

The hot sector in December is almost always a cold trade in the following year. Data since 1975.

Apr 16, 2026
DT
Dominic
Regime Bias: When Your Strategy Works in Bulls and Only Bulls
Trading Bias5 min

Regime Bias: When Your Strategy Works in Bulls and Only Bulls

A strategy tested on sunny days only. Then winter comes. Then your portfolio dies.

Apr 16, 2026
DT
Dominic
P-Hacking: 20 Random Strategies. One Looks Brilliant. By Luck Alone.
Trading Bias5 min

P-Hacking: 20 Random Strategies. One Looks Brilliant. By Luck Alone.

The math says if you test 20 strategies, one looks significant by pure chance. That one is usually what gets published.

Apr 16, 2026
DT
Dominic
Confirmation Bias: I Built 8 Strategy Variants. 6 Failed. Here's Why You Saw One.
Trading Bias5 min

Confirmation Bias: I Built 8 Strategy Variants. 6 Failed. Here's Why You Saw One.

The winners get published. The losers get deleted. A confession, and the cure.

Apr 16, 2026
DT
Dominic
Sunk Cost: 3 Years of XRP and the Most Expensive Feelings in Crypto
Trading Bias12 min

Sunk Cost: 3 Years of XRP and the Most Expensive Feelings in Crypto

My February 2021 journal said 'SELL'. I held until late 2023. Cost: $140,000 realized + $180,000 opportunity. The anatomy of a trapped bag.

Apr 16, 2026
DT
Dominic
Cherry Picking: The YouTube Guru Who Only Shows You 2020
Trading Bias5 min

Cherry Picking: The YouTube Guru Who Only Shows You 2020

Any strategy can look brilliant if you pick the right 12 months. Here's how to spot the trick.

Apr 15, 2026
DT
Dominic
Overfitting: Our Best Bot Made +45%, Then Lost 27% on Real Data
Trading Bias5 min

Overfitting: Our Best Bot Made +45%, Then Lost 27% on Real Data

16 months of data: gold nugget. 6 years of data: disaster. The difference between fit and edge.

Apr 15, 2026
DT
Dominic
Hindsight Bias: Why NVIDIA Was "Obvious" (Only After It Won)
Trading Bias5 min

Hindsight Bias: Why NVIDIA Was "Obvious" (Only After It Won)

In 2015, NVIDIA had the same metrics as Qualcomm, Intel, and IBM. Guess which won 100x.

Apr 15, 2026
DT
Dominic
FOMO: The $140,000 Tax I Paid Between 2019 and 2023
Trading Bias11 min

FOMO: The $140,000 Tax I Paid Between 2019 and 2023

Three FOMO trades. One tax bill. Here's exactly how Fear of Missing Out drained my portfolio — and the mechanical rules that now block it.

Apr 15, 2026
DT
Dominic
Look-Ahead Bias: When Your AI Knows Tomorrow's Newspaper
Trading Bias6 min

Look-Ahead Bias: When Your AI Knows Tomorrow's Newspaper

I spent $4.64 on 135 Claude analyses for a 7-year backtest. Result: -1.4 percentage points. Here's why.

Apr 14, 2026
DT
Dominic
Survivorship Bias: How Sandra's 14 "Perfect" Stocks Hid 12 Losers
Trading Bias6 min

Survivorship Bias: How Sandra's 14 "Perfect" Stocks Hid 12 Losers

+510% vs +28.5%. Same strategy. Same rules. 482 percentage points of pure survivorship bias.

Apr 14, 2026
DT
Dominic
Loss Aversion: Why Sandra Sold Every Winner Too Early
Trading Bias9 min

Loss Aversion: Why Sandra Sold Every Winner Too Early

The 2:1 pain asymmetry that Kahneman and Tversky documented — and how Odean found it draining 4.4% per year from retail accounts.

Apr 14, 2026
DT
Dominic
Why You Are Your Own Worst Enemy: 12 Behavioral Biases That Cost Retail Traders Everything
Trading Bias12 min

Why You Are Your Own Worst Enemy: 12 Behavioral Biases That Cost Retail Traders Everything

Your backtest is honest. Your trading is chaos. Here are the 12 biases that make real-money decisions different from paper ones.

Apr 13, 2026
DT
Dominic
Overconfidence: Your First 3 Winning Trades Are the Most Dangerous
Trading Bias10 min

Overconfidence: Your First 3 Winning Trades Are the Most Dangerous

At 55% win rate, 3-win streaks happen 17% of the time. Your brain reads them as mastery. Your account pays for the size-up that follows.

Apr 11, 2026
DT
Dominic
Anchoring: $100k Bitcoin Is Cheap (Said Everyone at $69k)
Trading Bias9 min

Anchoring: $100k Bitcoin Is Cheap (Said Everyone at $69k)

Tversky-Kahneman 1974. Every ATH becomes an anchor. Your brain hunts discounts against phantom reference points — and pays a real tax.

Apr 10, 2026
DT
Dominic
🪦

We don't have survivorship bias ourselves

Every bot we retired, every combo that failed walk-forward, every strategy that looked great until we ran the honest version — all documented publicly on one page.

See our failures →

The 10 biases covered in this series

1
Survivorship Bias
Picking winners after they won
2
Look-Ahead Bias
Using tomorrow's data to predict today
3
Hindsight Bias
"It was obvious, wasn't it?"
4
Overfitting
The bot that memorized the answers
5
Cherry Picking
Only showing your wins
6
Confirmation Bias
Saving only what you like
7
P-Hacking
Test enough, something "works"
8
Regime Bias
Bull-only testing
9
Recency Bias
Last year's winners = next year's?
10
Data-Snooping
Tuning parameters until it fits
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