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Cumulative distribution function

Probability that random variable X is less than or equal to x / From Wikipedia, the free encyclopedia

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In probability theory and statistics, the cumulative distribution function (CDF) of a real-valued random variable , or just distribution function of , evaluated at , is the probability that will take a value less than or equal to .[1]

Exponential_distribution_cdf.svg
Cumulative distribution function for the exponential distribution
Normal_Distribution_CDF.svg
Cumulative distribution function for the normal distribution

Every probability distribution supported on the real numbers, discrete or "mixed" as well as continuous, is uniquely identified by a right-continuous monotone increasing function (a càdlàg function) satisfying and .

In the case of a scalar continuous distribution, it gives the area under the probability density function from minus infinity to . Cumulative distribution functions are also used to specify the distribution of multivariate random variables.