Science & Engineering

Probability Calculator (Union, Intersection, Conditional)

Compute basic probability along with union, intersection, conditional, and at-least-one outcomes over n trials. The input fields change with the mode, and results show as percent, decimal, and a rough odds form.

How to use
  1. Pick the mode, such as union, intersection, or conditional.
  2. Enter the probabilities the mode asks for.
  3. Check the at-least-one figure across multiple trials.
Examples
Probability
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Decimal
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Fraction / odds
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Complement P(not)
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For study and estimation. Verify against authoritative data before relying on a result.
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How it's calculated

P = favorable ÷ total (single-event mode)

Modes: basic = favorable ÷ total; union = P(A)+P(B)−P(A∩B); independent = P(A)·P(B); conditional = P(A∩B)÷P(B); at-least-once over n tries = 1 − (1−p)ⁿ. Complement = 1 − P.

Common questions

What is the at-least-one probability?

It is the chance an event happens at least once over n trials, found as one minus the chance it never happens.

What does P(A|B) mean?

It is the conditional probability of A given that B has already happened, which the conditional mode computes for you.

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