HOW TO · PAPER PRACTICE

How to use Parlay Builder

Understand why the chance of several events all happening shrinks, and why dependence matters.

Before you start

Use independent imaginary events. This exercise models joint probability; it does not create an order or establish an offered payout.

Open Parlay Builder

Step by step

  1. Name two legs ‘Coin A heads’ and ‘Coin B heads’ and enter 50 in each Prob % field.
  2. Leave Your edge per leg (optional, %) blank for the basic exercise.
  3. Select Calculate Parlay and inspect the combined probability and theoretical payout multiple.
  4. Use + Add Leg to add a third independent 50% event, then calculate again.

Worked example

Two independent fair coins both land heads with probability 0.50 × 0.50 = 25%. Three give 12.5%. The reciprocal 4× for two coins is a mathematical fair gross multiple, not a promised market payout.

What the result means

Multiplication assumes independence. ‘It rains’ and ‘the ground gets wet’ cannot be treated like separate coin tosses. The optional edge field is another assumption, not evidence.

If something goes wrong

Use at least two legs and probabilities strictly between 0 and 100. If events share a cause, do not rely on this model for their combined chance.

Check your understanding

Try four independent 50% events. Verify 6.25%, then explain why adding a duplicate of the same event would not halve the real probability.