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VELNARO

Probability Calculator

Enter the probability of event A and event B to see the chance of both happening, either happening, neither happening, and exactly one happening.

Enter a value between 0 and 1 (or a percentage over 100).

P(A and B)

15%

P(A or B)

65%

P(neither)

35%

P(exactly one)

50%

P(not A)

50%

Odds in favour of A

1 : 1

How this was worked out

  1. Step 1P(A and B) = P(A) × P(B) = 0.5 × 0.3
  2. Step 2P(A or B) = P(A) + P(B) − P(A and B)
  3. Step 3P(neither) = 1 − P(A or B) = 0.35

Formula

Independent: P(A∩B) = P(A) × P(B) • P(A∪B) = P(A) + P(B) − P(A∩B) • P(neither) = 1 − P(A∪B)

Example

Input

P(A) = 0.5, P(B) = 0.3, independent

Result

P(A and B) = 15%, P(A or B) = 65%

Frequently asked questions

Independent events do not affect each other, so you multiply their probabilities. Mutually exclusive events cannot both happen, so P(A and B) = 0.

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