![]() If the presence of one individual affects the chance of other individuals occurring within that sampling unit, then this can lead to a negative binomial distribution. True clumping aggregation or contagion:.If colonies of individuals are distributed randomly over an area or over time, and the numbers of individuals within a colony follow a logarithmic distribution, then a count of individuals will follow a negative binomial distribution. Compounding of Poisson and logarithmic distributions:.If the mean of a Poisson distribution (λ) varies randomly from place to place or from time to time, under certain conditions the observed distribution of individuals from a mixture of several such Poisson distributions will follow a negative binomial distribution. If birth and death rates are constant, and there is a constant rate of immigration, then the population's size will follow a negative binomial distribution. Constant birth-death-immigration rates:.This model is the least relevant biologically, but the one given by most standard texts. If observations are selected at random, the number of observations in excess of k that are taken in order to obtain just k individuals with the character has a negative binomial distribution, with exponent k. Let a proportion P of individuals possess a certain character. However, unlike the normal distribution, the negative binomial does not naturally result from the use of large samples - nor does it arise from a single causal model.Īnscombe (1950) described 5 causal models of the negative binomial, some of which can be interpreted as due to aggregation: Also like the normal distribution, it can be completely defined by just two parameters - its mean (m) and shape parameter (k). It is commonly used to describe the distribution of count data, such as the numbers of parasites in blood specimens. The negative binomial distribution, like the normal distribution, arises from a mathematical formula.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |