Statistics calculator

Probability Calculator for Events

Calculate independent probability for A and B, A or B, and not A.

FormulaP(A and B) = P(A) x P(B); P(A or B) = P(A) + P(B) - P(A and B)

Formula

Independent probability

P(A and B) = P(A) x P(B); P(A or B) = P(A) + P(B) - P(A and B)

If A is 40% and B is 30%, both happen with 12% probability.

FAQ6 common questions for this calculator.

FAQs

Does this assume independence?+

Yes. It assumes event A and event B are independent.

What if events are not independent?+

Use conditional probability instead; this simple calculator will not model dependence.

How does the Probability Calculator calculate the result?+

For the Probability Calculator, it uses the Independent probability: P(A and B) = P(A) x P(B); P(A or B) = P(A) + P(B) - P(A and B). If A is 40% and B is 30%, both happen with 12% probability.

What information do I need to use the Probability Calculator?+

For the Probability Calculator, enter the known quantities requested by the calculator and use the units implied by the Independent probability. If a value is unknown, choose a calculator that solves for that specific variable.

How accurate is the Probability Calculator?+

Probability Calculator calculates the selected statistic from the sample values provided. It uses the Independent probability, but missing data, outliers, sample bias, and distribution assumptions can affect what the result means.

What should I check before using the Probability Calculator result?+

For the Probability Calculator, check the sample values, sample definition, missing values, outliers, and rounding precision. A statistic can be numerically correct but still describe a weak sample.

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Statistics guide

How to use the Probability Calculator

Calculate independent probability for A and B, A or B, and not A. The page also explains the independent probability and shows a practical example: If A is 40% and B is 30%, both happen with 12% probability.

  1. 1

    Enter your details

    Enter the values for the probability calculator scenario you want to check.

  2. 2

    Check the calculation

    Review the result alongside the independent probability: P(A and B) = P(A) x P(B); P(A or B) = P(A) + P(B) - P(A and B).

  3. 3

    Compare scenarios

    Change one or more inputs to see how they affect the probability Calculator result before you use the estimate.