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I BeginnerWeek 1 • Lesson 1Duration: 30 min

QNT What Is Quantitative Trading?

From gut feeling to math-backed edge — why the shift matters

Learning Objectives

  • Know the difference between discretionary and systematic trading
  • Define alpha and edge in concrete, measurable terms
  • See the three things every working quant system needs
  • Understand how institutional firms actually approach markets

Explain Like I'm 5

Imagine you find a coin that lands on heads 59 out of 100 flips. Any single flip is a coin toss. But over thousands of flips, math guarantees you come out ahead. Quant trading works the same way — find situations where the odds favor you, then exploit that edge thousands of times while managing your risk.

Think of It This Way

Think of it like running a casino instead of gambling in one. A gambler hopes to win any single hand. The casino doesn't worry about individual hands — they rely on math across millions of plays. Good quant systems work the same way: consistent edge, compounded over many trades.

1How Trading Got Here

Trading went through three big shifts. Before the 1970s — Discretionary. Traders used gut instinct, chart patterns, and whatever information they could get. Decisions were subjective and inconsistent. 1970s–2000s — Quantitative Methods. Black-Scholes (1973), CAPM, and the first algorithmic execution strategies brought math into trading. Statistical arbitrage started at Morgan Stanley in the 1980s under Nunzio Tartaglia's group. 2000s–Now — ML and Big Data. Modern systems combine machine learning with massive datasets to find patterns no human could spot. Renaissance Technologies, Two Sigma, and DE Shaw manage hundreds of billions this way. Today's institutional systems typically use multi-layer ML pipelines: one layer finds candidate signals, another filters for timing, and a third manages exits. This separation of concerns — borrowed from software engineering — lets each piece be optimized for its specific job.

Growth of Algorithmic Trading (% of Market Volume)

2What "Edge" Actually Means

Edge is a statistical advantage. Over enough trades, it produces positive returns. That's it. The word to focus on is statistical. Any single trade can lose. What matters is the distribution across hundreds or thousands of trades. People get confused here. Edge doesn't mean winning every trade. It means the math favors you over time: • A 59% win rate means roughly 4 out of every 7 trades are profitable • Positive expected R means each unit of risk produces net positive return • Smart risk management amplifies this — cut losses quickly, let winners run • Adapting to market conditions keeps the edge from degrading The core idea is simple: a small edge, applied consistently over many trades with proper risk management, produces real returns. That's just the Law of Large Numbers applied to financial markets. Reference: Thorp, E.O. (2006). "The Kelly Criterion in Blackjack, Sports Betting, and the Stock Market."

How Small Edge Compounds Over 1,000 Trades

3The Three Things Every Quant System Needs

There are three pieces that have to work together. Take away any one and the system breaks. 1. Signal Generation — When to trade. Use data and ML to find moments where the probability of a profitable trade crosses a meaningful threshold. Modern systems process dozens of features per bar — price action, momentum, volatility, microstructure data — to generate candidate signals. 2. Execution Management — How to trade. Get in at the right price with the right size, manage the trade through exit. This includes timing filters (which reject poorly-timed signals) and dynamic exit management based on what the market is doing right now. 3. Risk Management — How much to risk. Make sure no single loss — or streak of losses — can blow your account. Position sizing rules, drawdown-triggered scaling, and strict loss limits handle this. Here's the thing people miss: a great signal with bad risk management leads to ruin. Great risk management with no signal leads to slow bleeding. Both have to work together. Execution bridges the gap — it turns good signals into well-managed trades.
[Diagram]

Diagram: sketch this architecture to solidify your understanding

Key Formulas

Expected Value per Trade

WR is win rate, W̄ is average win in R-multiples, L̄ is average loss. If E[R] is positive, you have an edge. If it's negative, no optimization will save you. This is the single most important formula in trading.

Kelly Criterion (Optimal Position Sizing)

p is win probability, q = 1 − p, b is win/loss ratio. This gives the theoretically optimal fraction of capital to risk per trade. In practice, most quants use fractional Kelly (0.25× to 0.5×) because full Kelly is too volatile for real accounts.

Hands-On Code

Computing Expected Value — The Foundation of Edge

python
import numpy as np

# --- Expected Value Calculation ---
# Representative parameters for a well-calibrated
# multi-layer ML trading system.

win_rate   = 0.592    # 59.2% of trades are profitable
avg_win_r  = 1.65     # Average winner: +1.65R
avg_loss_r = 0.95     # Average loser:  -0.95R

# Expected value per trade
ev = (win_rate * avg_win_r) - ((1 - win_rate) * avg_loss_r)
print(f"Expected R per trade: {ev:+.3f}R")

# Over N trades, the Law of Large Numbers takes effect
n_trades = 4500
total_expected = ev * n_trades
print(f"Expected total over {n_trades:,} trades: {total_expected:+.1f}R")

# Kelly fraction for position sizing
b = avg_win_r / avg_loss_r  # payoff ratio
kelly = (win_rate * b - (1 - win_rate)) / b
print(f"Full Kelly fraction: {kelly:.3f}")
print(f"Quarter Kelly (safer): {kelly / 4:.4f}")

This shows the core idea: positive expected value per trade, compounded across thousands of trades, adds up. Kelly Criterion gives the theoretical ceiling for sizing, but conservative practitioners use a fraction to keep drawdowns manageable.

Knowledge Check

Q1.What is the defining characteristic of a quantitative trading edge?

Q2.A strategy has a 55% win rate with 1:1 risk-reward. Is the expected value positive?

Q3.Which of the three pillars of quantitative trading is most commonly neglected by retail traders?

Assignment

Calculate the expected value for a strategy with 52% win rate, average win of 2.0R, and average loss of 1.0R. Then figure out: (a) how many trades you need for the edge to become statistically significant at p < 0.05, and (b) the Kelly-optimal position size. Show your code and explain each step.