independent identically distributed
Two random variables and are said to be identically distributed if they are defined on the same probability space
, and the distribution function
of and the distribution function of are the same: . When and are identically distributed, we write .
A set of random variables , in some index set , is identically distributed if for every pair .
A collection of random variables () is said to be independent identically distributed, if the ’s are identically distributed, and mutually independent
(http://planetmath.org/Independent) (every finite subfamily of is independent). This is often abbreviated as iid.
For example, the interarrival times of a Poisson process of rate are independent and each have an exponential distribution with mean , so the are independent identically distributed random variables.
Many other examples are found in statistics, where individual data points are often assumed to realizations of iid random variables.