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
Growth of Algorithmic Trading (% of Market Volume)
2What "Edge" Actually Means
How Small Edge Compounds Over 1,000 Trades
3The Three Things Every Quant System Needs
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
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.