Build Your Distribution
In a valid probability distribution, all probabilities must sum to exactly 1.0 (100%).
Win ${{ outcome.val }}
P = {{ probs[idx].toFixed(2) }}
{{ totalProb.toFixed(2) }}
Slide to 1.0
Build Expected Value
Expected Value is the sum of each outcome multiplied by its probability.
Your Distribution
Outcome (X)
Prob P(X)
${{ outcome.val }}
{{ probs[idx].toFixed(2) }}
${{ slot.x.val }}
X
{{ slot.p.val }}
P(X)
+
+
Equation Built!
${{ item.val }}
Drag to multiply
Calculate the Average
Tap each component to calculate its value, then sum them up.
${{ expectedValue.toFixed(2) }}
Tap to calculate
Design a Fair Game
A game is fair if the Expected Profit is exactly $0. Adjust the ticket cost.
Expected Payout E(X)
${{ expectedValue.toFixed(2) }}
Ticket Cost
${{ ticketCost.toFixed(2) }}
Expected Profit
+
-
${{ Math.abs(profit).toFixed(2) }}
Fair Game! ⚖️
Player Advantage
House Advantage
Adjust to fair
🎉
You Mastered Expected Value!
You successfully built a probability distribution, calculated the long-run average payout, and designed a fair game.