Binomial probability mass function

Gives the probability of observing exactly x successes in n independent trials, each with success probability p. It is used for counting successes in a fixed number of yes/no experiments.

P(X = x) = \binom{n}{x} p^x (1 - p)^{n - x}

What the symbols mean

discrete random variable counting the number of successes
number of successes observed, an integer from 0 to n
number of independent trials
probability of success on each trial, between 0 and 1
binomial coefficient, the number of ways to choose x successes among n trials

About this formula

  • FieldMathematics
  • TopicProbability distributions
  • LevelUniversity
  • Also calledbinomial distribution formula, binomial probability formula, probability of k successes in n trials, binomial pmf, bernoulli trials probability, binomial coefficient probability
  • SourceWikidata Q185547

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