Probability mass function: Difference between revisions

Revision as of 23:38, 24 June 2007

Revision as of 10:46, 19 July 2007

Line 1:

[[Image:Discrete probability distrib.png|right|thumb|The graph of a probability mass function. All the values of this function must be non-negative and sum up to 1.]]

In [[probability theory]], a '''probability mass function''' (abbreviated '''pmf''') is a function that gives the probability that a [[discrete random variable|discrete]] [[random variable]] is exactly equal to some value. A probability mass function differs from a [[probability density function]] (abbreviated '''pdf''') in that the values of a pdf, defined only for [[continuous random variable]]s, are not probabilities; ratheras such. Instead, itsthe integral of a pdf over a setrange of possible values <nowiki>[</nowiki>a, b) gives the probability of the random variable isfalling awithin probabilitythat range.

==Mathematical description==