"If there's an 84% chance of rain in an hour, what's the probability of rain in half an hour?"

That's the SIG question that broke my brain. I sat there for 2 minutes trying to remember some obscure probability formula before realizing it was testing whether I understood exponential decay.

(The answer is 60%, by the way. If p = 1 - e^(-λt), then solving backwards gives you the rate.)

Here's everything I learned about SIG's Quant Evaluation after taking it twice and finally passing.

Practice the test format: Try our SIG Math Test simulator here.

The Real Test Format

You get Mettl's testing platform, 20 minutes, and questions that make you doubt everything you know about probability.

The Questions That Everyone Gets Wrong

Based on actual test-taker reports from 2024:

The Nursery Problem (Classic SIG)

"A woman gives birth. The baby is placed in a nursery with other babies. A nurse picks up a random baby - it's a boy. What's the probability the woman gave birth to a boy?"

Most people say 50%. They're wrong. It's 60%.

Think about it: If the woman had a girl, the nurse could only pick boys from the existing nursery babies. If the woman had a boy, there's one extra boy to pick. Bayes theorem in disguise.

The Dice Game Trap

"You roll a die and win the amount shown. But you can roll again if you want, taking the second result. What's the fair price for this game?"

Expected value of one roll: 3.5 But you'll only reroll if you get 1, 2, or 3. So: 0.5 × 3.5 + 0.5 × 5 = 4.25

Half the test-takers forget you only reroll bad outcomes.

The Printer Jam Special

"Three printers jam independently: 25%, 20%, 15% of the time. What's the probability exactly two jam today?"

This is just binomial probability in a trench coat: P(A,B,not C) + P(A,not B,C) + P(not A,B,C) = 0.25×0.20×0.85 + 0.25×0.80×0.15 + 0.75×0.20×0.15 = 8.5%

What SIG Actually Tests (Hint: It's Not Just Math)

They're testing whether you can think like a trader. Every question has a trick, and the trick is usually: "Did you think about this the right way?"

Expected Value Problems (40% of test)

These come in every flavor:

• Casino games with weird rules
• Investment decisions under uncertainty
• "Should you play this game?" setups

The Meta Strategy: If EV > 0, always say yes. If EV < 0, check if there's a twist (like optional rerolls or early stopping).

Conditional Probability (30% of test)

Always Bayes' theorem in disguise:

• Medical test accuracy problems
• "Given X happened, what's P(Y)?"
• Sequential event problems

Red flag words: "given that", "knowing that", "if we observe"

Combinatorics (20% of test)

Usually simple but with large numbers:

• "How many ways to arrange..."
• "Probability of specific sequence..."
• Card problems with multiple draws

Calculator saves you here: Just compute C(n,k) directly.

Logic Puzzles (10% of test)

The curveballs:

• Correlation questions ("If cor(X,Y)=0.9 and cor(Y,Z)=0.9, what's cor(X,Z)?")
• Paradoxes and counterintuitive results
• "Find the flaw in this reasoning"

How to Actually Prepare (Without Reading the Green Book)

Everyone says "study the green book." Here's what actually works:

Week 1: Build Intuition

Forget formulas. Work through these patterns until they're automatic:

• If events are independent: P(A and B) = P(A) × P(B)
• If you're counting arrangements: Order matters = permutation
• If you see "at least one": Calculate 1 - P(none)
• If you see "given that": It's Bayes, set up the tree

Practice on brilliant.org's probability section. Way better than textbooks.

Week 2: SIG-Specific Prep

Their questions have a style. Practice these exact formats:

• Games where you can stop/reroll (always involves comparing EVs)
• Problems with missing information that doesn't matter
• "What's wrong with this reasoning?" setups
• Exponential processes (like the rain problem)

The Day Before

Do NOT cram new concepts. Just review these golden rules:

1. Independent events multiply
2. Expected value is linear
3. Conditional probability ≠ joint probability
4. Check your answer makes intuitive sense

What Happens After the Test

Pass the quant eval? Congrats, now the real pain begins:

Next up: HR phone screen with probability brainteasers. Yes, more probability. They really love this stuff.

Then: Technical interviews where they ask you to price options using the probability concepts from the test.

Finally: The dreaded "chip game" where you trade with poker chips while they mess with your head.

But that's all after you pass this test. Focus on getting 13+ correct first.

Test Day Strategy That Actually Works

Before You Start

• Use Chrome. Their system hates Safari.
• Close everything. Even Spotify. Paranoid system.
• Have paper ready. You'll need to draw probability trees.
• Calculator open. Phone calculator is fine.

During the Test

Read every question twice. SIG loves hiding important details in the middle of paragraphs. "The coin is fair" might appear three sentences after they introduce the coin.

If you're stuck after 90 seconds, guess and move on. You can come back. Most people get stuck on question 3 or 4 (it's always a weird one) and waste 5 minutes.

The Guessing Game

No penalty for wrong answers = guess aggressively. But guess smart:

• Probability answers are usually "nice" numbers (1/4, 2/3, not 0.3749)
• Expected values often end in .25 or .5
• If two answers are reciprocals (like 2/3 and 3/2), one is probably right

Why SIG Obsesses Over Probability

Real trading at SIG is just applied probability. Every day traders face questions like:

• "This option is mispriced. What's the probability we're wrong?"
• "Should we hedge this position? What's the expected cost vs. risk?"
• "Market's down 2%. Is this noise or a trend?"

The math test checks if you think probabilistically by instinct, not formula.

One Candidate's Story

"I failed the first time. Got cocky, didn't prepare, figured my math degree would carry me. The questions weren't hard mathematically - I just kept missing the tricks.

Second attempt, I spent two weeks doing every practice problem I could find. Not memorizing formulas, but learning to spot the patterns. When I saw the nursery problem again, I smiled.

Got 14/16. Now I work there. The test is learnable."

Your Move

SIG's test is a filter, but a fair one. They're not testing IQ or math contest skills. They're testing whether you can think clearly about uncertainty.

If that sounds like you, put in the two weeks of prep and take your shot.

Ready to practice? Start with our SIG Math Test simulator featuring realistic probability questions from actual test-takers.