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Statistics vocabulary · Probability Distributions

Poisson distribution

Meaning in statistics, with examples

nounAdvanced term

In statistics, Poisson distribution means: A probability distribution for the number of times an event happens in a fixed period or space when events occur independently at a constant average rate.

In Turkish: Poisson dağılımı

How it is used

Used for counts such as calls per hour, accidents per month or typos per page. Its single parameter λ (lambda) is both the mean and the variance; when the variance is clearly larger, analysts talk about 'overdispersion'. Named after the French mathematician Siméon Denis Poisson.

Example sentences

  1. The number of emergency calls per hour follows a Poisson distribution with a mean of 4.

  2. The variance is far bigger than the mean, so a Poisson distribution doesn't fit these data well.

Common collocations

  • Poisson process
  • Poisson regression
  • follow a Poisson distribution
  • rate parameter lambda
  • binomial distributionThe probability distribution of the number of successes in a fixed number of independent trials, each with the same probability of success, such as heads in 20 coin tosses.
  • distributionThe pattern showing which values a variable takes and how often each one occurs, often pictured as a histogram or a curve.
  • varianceThe average of the squared distances between each value and the mean; it measures spread, and its square root is the standard deviation.
  • expected valueThe long-run average result of a random variable if the same process were repeated many times, found by weighting each possible value by its probability.

More terms: Probability Distributions

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