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fix: align ev-calculator tests with decimal (0-1) probability format

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The implementation and rest of the system (ICM calculator, probability
updater) use decimals (0-1) for probabilities, but the tests were using
percentages (0-100). Updated tests and docs to match.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Chris Parsons 2026-02-14 23:26:32 -08:00
parent 24126fe389
commit 96b4c5a350
2 changed files with 144 additions and 148 deletions
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273
app/services/__tests__/ev-calculator.test.ts
View file

@ -22,56 +22,56 @@ describe("calculateEV", () => {
it("should calculate EV for equal probabilities", () => {
const probabilities: ProbabilityDistribution = {
probFirst: 12.5,
probSecond: 12.5,
probThird: 12.5,
probFourth: 12.5,
probFifth: 12.5,
probSixth: 12.5,
probSeventh: 12.5,
probEighth: 12.5,
probFirst: 0.125,
probSecond: 0.125,
probThird: 0.125,
probFourth: 0.125,
probFifth: 0.125,
probSixth: 0.125,
probSeventh: 0.125,
probEighth: 0.125,
};
const ev = calculateEV(probabilities, defaultScoring);
// EV = 12.5% × (100+70+50+40+25+25+15+15) = 12.5% × 340 = 42.5
// EV = 0.125 × (100+70+50+40+25+25+15+15) = 0.125 × 340 = 42.5
expect(ev).toBe(42.5);
});
it("should calculate EV for favorite (high probability of 1st)", () => {
const probabilities: ProbabilityDistribution = {
probFirst: 50,
probSecond: 30,
probThird: 10,
probFourth: 5,
probFifth: 3,
probSixth: 1,
probSeventh: 0.5,
probEighth: 0.5,
probFirst: 0.50,
probSecond: 0.30,
probThird: 0.10,
probFourth: 0.05,
probFifth: 0.03,
probSixth: 0.01,
probSeventh: 0.005,
probEighth: 0.005,
};
const ev = calculateEV(probabilities, defaultScoring);
// EV = 50% × 100 + 30% × 70 + 10% × 50 + 5% × 40 + 3% × 25 + 1% × 25 + 0.5% × 15 + 0.5% × 15
// EV = 0.50×100 + 0.30×70 + 0.10×50 + 0.05×40 + 0.03×25 + 0.01×25 + 0.005×15 + 0.005×15
// = 50 + 21 + 5 + 2 + 0.75 + 0.25 + 0.075 + 0.075 = 79.15
expect(ev).toBe(79.15);
});
it("should calculate EV for underdog (low probability of 1st)", () => {
const probabilities: ProbabilityDistribution = {
probFirst: 2,
probSecond: 5,
probThird: 8,
probFourth: 10,
probFifth: 15,
probSixth: 20,
probSeventh: 20,
probEighth: 20,
probFirst: 0.02,
probSecond: 0.05,
probThird: 0.08,
probFourth: 0.10,
probFifth: 0.15,
probSixth: 0.20,
probSeventh: 0.20,
probEighth: 0.20,
};
const ev = calculateEV(probabilities, defaultScoring);
// EV = 2% × 100 + 5% × 70 + 8% × 50 + 10% × 40 + 15% × 25 + 20% × 25 + 20% × 15 + 20% × 15
// EV = 0.02×100 + 0.05×70 + 0.08×50 + 0.10×40 + 0.15×25 + 0.20×25 + 0.20×15 + 0.20×15
// = 2 + 3.5 + 4 + 4 + 3.75 + 5 + 3 + 3 = 28.25
expect(ev).toBe(28.25);
});
@ -89,26 +89,26 @@ describe("calculateEV", () => {
};
const probabilities: ProbabilityDistribution = {
probFirst: 20,
probSecond: 20,
probThird: 15,
probFourth: 15,
probFifth: 10,
probSixth: 10,
probSeventh: 5,
probEighth: 5,
probFirst: 0.20,
probSecond: 0.20,
probThird: 0.15,
probFourth: 0.15,
probFifth: 0.10,
probSixth: 0.10,
probSeventh: 0.05,
probEighth: 0.05,
};
const ev = calculateEV(probabilities, customScoring);
// EV = 20% × 200 + 20% × 150 + 15% × 100 + 15% × 80 + 10% × 50 + 10% × 50 + 5% × 30 + 5% × 30
// EV = 0.20×200 + 0.20×150 + 0.15×100 + 0.15×80 + 0.10×50 + 0.10×50 + 0.05×30 + 0.05×30
// = 40 + 30 + 15 + 12 + 5 + 5 + 1.5 + 1.5 = 110
expect(ev).toBe(110);
});
it("should handle 100% probability of one placement (finished participant)", () => {
const probabilities: ProbabilityDistribution = {
probFirst: 100,
probFirst: 1.0,
probSecond: 0,
probThird: 0,
probFourth: 0,
@ -119,24 +119,24 @@ describe("calculateEV", () => {
};
const ev = calculateEV(probabilities, defaultScoring);
expect(ev).toBe(100); // 100% × 100 = 100
expect(ev).toBe(100); // 1.0 × 100 = 100
});
it("should handle probabilities with decimal places", () => {
const probabilities: ProbabilityDistribution = {
probFirst: 15.75,
probSecond: 14.25,
probThird: 13.50,
probFourth: 12.75,
probFifth: 11.00,
probSixth: 10.50,
probSeventh: 11.25,
probEighth: 11.00,
probFirst: 0.1575,
probSecond: 0.1425,
probThird: 0.1350,
probFourth: 0.1275,
probFifth: 0.1100,
probSixth: 0.1050,
probSeventh: 0.1125,
probEighth: 0.1100,
};
const ev = calculateEV(probabilities, defaultScoring);
// EV = 15.75% × 100 + 14.25% × 70 + ... = 46.29
// EV = 0.1575×100 + 0.1425×70 + ... = 46.29
expect(ev).toBeCloseTo(46.29, 2);
});
@ -158,31 +158,31 @@ describe("calculateEV", () => {
});
describe("validateProbabilities", () => {
it("should validate probabilities that sum to 100", () => {
it("should validate probabilities that sum to 1.0", () => {
const valid: ProbabilityDistribution = {
probFirst: 20,
probSecond: 20,
probThird: 15,
probFourth: 15,
probFifth: 10,
probSixth: 10,
probSeventh: 5,
probEighth: 5,
probFirst: 0.20,
probSecond: 0.20,
probThird: 0.15,
probFourth: 0.15,
probFifth: 0.10,
probSixth: 0.10,
probSeventh: 0.05,
probEighth: 0.05,
};
expect(validateProbabilities(valid)).toBe(true);
});
it("should accept probabilities within tolerance (default 0.1%)", () => {
it("should accept probabilities within tolerance (default 0.01)", () => {
const nearlyValid: ProbabilityDistribution = {
probFirst: 20.05,
probSecond: 20,
probThird: 15,
probFourth: 15,
probFifth: 10,
probSixth: 10,
probSeventh: 5,
probEighth: 4.95,
probFirst: 0.2005,
probSecond: 0.20,
probThird: 0.15,
probFourth: 0.15,
probFifth: 0.10,
probSixth: 0.10,
probSeventh: 0.05,
probEighth: 0.0495,
};
expect(validateProbabilities(nearlyValid)).toBe(true);
@ -190,14 +190,14 @@ describe("validateProbabilities", () => {
it("should reject probabilities that sum too high", () => {
const tooHigh: ProbabilityDistribution = {
probFirst: 20,
probSecond: 20,
probThird: 20,
probFourth: 20,
probFifth: 10,
probSixth: 10,
probSeventh: 5,
probEighth: 5,
probFirst: 0.20,
probSecond: 0.20,
probThird: 0.20,
probFourth: 0.20,
probFifth: 0.10,
probSixth: 0.10,
probSeventh: 0.05,
probEighth: 0.05,
};
expect(validateProbabilities(tooHigh)).toBe(false);
@ -205,14 +205,14 @@ describe("validateProbabilities", () => {
it("should reject probabilities that sum too low", () => {
const tooLow: ProbabilityDistribution = {
probFirst: 10,
probSecond: 10,
probThird: 10,
probFourth: 10,
probFifth: 10,
probSixth: 10,
probSeventh: 5,
probEighth: 5,
probFirst: 0.10,
probSecond: 0.10,
probThird: 0.10,
probFourth: 0.10,
probFifth: 0.10,
probSixth: 0.10,
probSeventh: 0.05,
probEighth: 0.05,
};
expect(validateProbabilities(tooLow)).toBe(false);
@ -220,88 +220,87 @@ describe("validateProbabilities", () => {
it("should allow custom tolerance", () => {
const probabilities: ProbabilityDistribution = {
probFirst: 21,
probSecond: 20,
probThird: 15,
probFourth: 15,
probFifth: 10,
probSixth: 10,
probSeventh: 5,
probEighth: 4,
probFirst: 0.21,
probSecond: 0.20,
probThird: 0.15,
probFourth: 0.15,
probFifth: 0.10,
probSixth: 0.10,
probSeventh: 0.05,
probEighth: 0.04,
};
// Sum is 100, but with 1% tolerance
expect(validateProbabilities(probabilities, 1)).toBe(true);
// With stricter 0.1% tolerance
expect(validateProbabilities(probabilities, 0.1)).toBe(true);
// Sum is 1.0, within any tolerance
expect(validateProbabilities(probabilities, 0.01)).toBe(true);
expect(validateProbabilities(probabilities, 0.001)).toBe(true);
});
});
describe("normalizeProbabilities", () => {
it("should normalize probabilities that sum to more than 100", () => {
it("should normalize probabilities that sum to more than 1.0", () => {
const input: ProbabilityDistribution = {
probFirst: 22,
probSecond: 22,
probThird: 17,
probFourth: 17,
probFifth: 11,
probSixth: 11,
probSeventh: 5.5,
probEighth: 5.5,
probFirst: 0.22,
probSecond: 0.22,
probThird: 0.17,
probFourth: 0.17,
probFifth: 0.11,
probSixth: 0.11,
probSeventh: 0.055,
probEighth: 0.055,
};
// Sum = 111
// Sum = 1.11
const normalized = normalizeProbabilities(input);
// Each should be scaled down by 100/111
expect(normalized.probFirst).toBeCloseTo(19.82, 2);
expect(normalized.probSecond).toBeCloseTo(19.82, 2);
// Each should be scaled down by 1/1.11
expect(normalized.probFirst).toBeCloseTo(0.1982, 3);
expect(normalized.probSecond).toBeCloseTo(0.1982, 3);
// Sum should be exactly 100 (within rounding)
// Sum should be exactly 1.0 (within rounding)
const sum = Object.values(normalized).reduce((a, b) => a + b, 0);
expect(sum).toBeCloseTo(100, 1);
expect(sum).toBeCloseTo(1.0, 3);
});
it("should normalize probabilities that sum to less than 100", () => {
it("should normalize probabilities that sum to less than 1.0", () => {
const input: ProbabilityDistribution = {
probFirst: 18,
probSecond: 18,
probThird: 13.5,
probFourth: 13.5,
probFifth: 9,
probSixth: 9,
probSeventh: 4.5,
probEighth: 4.5,
probFirst: 0.18,
probSecond: 0.18,
probThird: 0.135,
probFourth: 0.135,
probFifth: 0.09,
probSixth: 0.09,
probSeventh: 0.045,
probEighth: 0.045,
};
// Sum = 90
// Sum = 0.90
const normalized = normalizeProbabilities(input);
// Each should be scaled up by 100/90
expect(normalized.probFirst).toBeCloseTo(20, 1);
expect(normalized.probSecond).toBeCloseTo(20, 1);
// Each should be scaled up by 1/0.90
expect(normalized.probFirst).toBeCloseTo(0.20, 2);
expect(normalized.probSecond).toBeCloseTo(0.20, 2);
const sum = Object.values(normalized).reduce((a, b) => a + b, 0);
expect(sum).toBeCloseTo(100, 1);
expect(sum).toBeCloseTo(1.0, 3);
});
it("should handle probabilities that already sum to 100", () => {
it("should handle probabilities that already sum to 1.0", () => {
const input: ProbabilityDistribution = {
probFirst: 20,
probSecond: 20,
probThird: 15,
probFourth: 15,
probFifth: 10,
probSixth: 10,
probSeventh: 5,
probEighth: 5,
probFirst: 0.20,
probSecond: 0.20,
probThird: 0.15,
probFourth: 0.15,
probFifth: 0.10,
probSixth: 0.10,
probSeventh: 0.05,
probEighth: 0.05,
};
const normalized = normalizeProbabilities(input);
// Should remain essentially unchanged
expect(normalized.probFirst).toBeCloseTo(20, 1);
expect(normalized.probSecond).toBeCloseTo(20, 1);
expect(normalized.probFirst).toBeCloseTo(0.20, 3);
expect(normalized.probSecond).toBeCloseTo(0.20, 3);
});
it("should handle all zeros by returning equal probabilities", () => {
@ -318,10 +317,10 @@ describe("normalizeProbabilities", () => {
const normalized = normalizeProbabilities(input);
// Should return 12.5% for each (equal distribution)
expect(normalized.probFirst).toBe(12.5);
expect(normalized.probSecond).toBe(12.5);
expect(normalized.probEighth).toBe(12.5);
// Should return 0.125 for each (equal distribution)
expect(normalized.probFirst).toBe(0.125);
expect(normalized.probSecond).toBe(0.125);
expect(normalized.probEighth).toBe(0.125);
});
});

19
app/services/ev-calculator.ts
View file

@ -21,10 +21,10 @@ export interface ScoringRules {
/**
* Probability distribution for a participant's placements
* All values should be percentages (0-100) and sum to ~100
* All values should be decimals (0-1) and sum to ~1.0
*/
export interface ProbabilityDistribution {
probFirst: number; // e.g., 15.5 means 15.5%
probFirst: number; // e.g., 0.155 means 15.5%
probSecond: number;
probThird: number;
probFourth: number;
@ -39,14 +39,14 @@ export interface ProbabilityDistribution {
*
* EV = Σ (probability × points) for each placement
*
* @param probabilities - Probability distribution (percentages 0-100)
* @param probabilities - Probability distribution (decimals 0-1)
* @param scoringRules - League's point values for each placement
* @returns Expected value (average projected points)
*
* @example
* ```ts
* const ev = calculateEV(
* { probFirst: 20, probSecond: 15, probThird: 12, ..., probEighth: 5 },
* { probFirst: 0.20, probSecond: 0.15, probThird: 0.12, ..., probEighth: 0.05 },
* { pointsFor1st: 100, pointsFor2nd: 70, ..., pointsFor8th: 15 }
* );
* // Returns: 45.5 (expected points)
@ -56,7 +56,6 @@ export function calculateEV(
probabilities: ProbabilityDistribution,
scoringRules: ScoringRules
): number {
// Probabilities are already decimals (0-1), no need to divide by 100
const ev =
probabilities.probFirst * scoringRules.pointsFor1st +
probabilities.probSecond * scoringRules.pointsFor2nd +
@ -71,11 +70,11 @@ export function calculateEV(
}
/**
* Validate that probability distribution sums to approximately 100%
* Validate that probability distribution sums to approximately 1.0
* (allows small rounding errors)
*
* @param probabilities - Probability distribution to validate
* @param tolerance - Acceptable deviation from 100% (default 0.1%)
* @param tolerance - Acceptable deviation from 1.0 (default 0.01)
* @returns true if valid, false otherwise
*/
export function validateProbabilities(
@ -92,7 +91,6 @@ export function validateProbabilities(
probabilities.probSeventh +
probabilities.probEighth;
// Validate sum is close to 1.0 (decimals, not percentages)
return Math.abs(sum - 1.0) <= tolerance;
}
@ -101,7 +99,7 @@ export function validateProbabilities(
* Useful when importing odds or dealing with rounding errors
*
* @param probabilities - Probability distribution to normalize
* @returns Normalized probabilities that sum to 1.0 (decimals, not percentages)
* @returns Normalized probabilities that sum to 1.0
*/
export function normalizeProbabilities(
probabilities: ProbabilityDistribution
@ -117,7 +115,7 @@ export function normalizeProbabilities(
probabilities.probEighth;
if (sum === 0) {
// Avoid division by zero - return equal probabilities (1/8 = 0.125 = 12.5%)
// Avoid division by zero - return equal probabilities (1/8 = 0.125)
return {
probFirst: 0.125,
probSecond: 0.125,
@ -130,7 +128,6 @@ export function normalizeProbabilities(
};
}
// Normalize to sum = 1.0 (decimals, not percentages)
const factor = 1.0 / sum;
return {