Poisson sampling
{{Short description|Survey methodology process}}
{{distinguish|Poisson disk sampling}}
In survey methodology, Poisson sampling (sometimes denoted as PO sampling{{rp|61}}) is a sampling process where each element of the population is subjected to an independent Bernoulli trial which determines whether the element becomes part of the sample.{{cite book
|title = Model Assisted Survey Sampling
|author=Carl-Erik Sarndal |author2=Bengt Swensson |author3=Jan Wretman
|isbn= 978-0-387-97528-3
|year = 1992
Each element of the population may have a different probability of being included in the sample (). The probability of being included in a sample during the drawing of a single sample is denoted as the first-order inclusion probability of that element (). If all first-order inclusion probabilities are equal, Poisson sampling becomes equivalent to Bernoulli sampling, which can therefore be considered to be a special case of Poisson sampling.
A mathematical consequence of Poisson sampling
Mathematically, the first-order inclusion probability of the ith element of the population is denoted by the symbol and the second-order inclusion probability that a pair consisting of the ith and jth element of the population that is sampled is included in a sample during the drawing of a single sample is denoted by .
The following relation is valid during Poisson sampling when :
:
is defined to be .