| NChapman {recapr} | R Documentation |
Chapman Estimator
Description
Calculates the value of the Chapman estimator for abundance in a mark-recapture experiment, with given values of sample sizes and number of recaptures. The Chapman estimator (Chapman modification of the Petersen estimator) typically outperforms the Petersen estimator, even though the Peterson estimator is the MLE.
Usage
NChapman(n1, n2, m2)
Arguments
n1 |
Number of individuals captured and marked in the first sample. This may be a single number or vector of values. |
n2 |
Number of individuals captured in the second sample. This may be a single number or vector of values. |
m2 |
Number of marked individuals recaptured in the second sample. This may be a single number or vector of values. |
Value
The value of the Chapman estimator, calculated as (n1+1)*(n2+1)/(m2+1) - 1
Note
Any Petersen-type estimator (such as this) depends on a set of assumptions:
The population is closed; that is, that there are no births, deaths, immigration, or emigration between sampling events
All individuals have the same probability of capture in one of the two events, or complete mixing occurs between events
Marking in the first event does not affect probability of recapture in the second event
Individuals do not lose marks between events
All marks will be reported in the second event
Author(s)
Matt Tyers
References
Chapman, D.G. (1951). Some properties of the hypergeometric distribution with applications to zoological censuses. Univ. Calif. Public. Stat. 1, 131-60.
See Also
NPetersen, NBailey, vChapman, seChapman, rChapman, pChapman, powChapman, ciChapman
Examples
NChapman(n1=100, n2=100, m2=20)