vstrat {recapr}

Estimated Variance of Stratified Abundance Estimator

Description

Calculates the estimated variance of the stratified estimator for abundance in a mark-recapture experiment, from vectors of sample sizes and number of recaptures, with each element corresponding to each sampling stratum.

Usage

vstrat(n1, n2, m2, estimator = "Chapman")

Arguments

n1

Vector of individuals captured and marked in the first sample, from each stratum

n2

Vector of individuals captured and marked in the second sample, from each stratum

m2

Vector of marked individuals recaptured in the second sample, from each stratum

estimator

The type of estimator to use. Allowed values are "Chapman", "Petersen", and "Bailey". Default to "Chapman".

Value

The estimated variance of the stratified estimator

Note

It is possible that even the stratified estimate of abundance may be biased if capture probabilities differ greatly between strata. However, the bias in the stratified estimator will be much less than an estimator calculated without stratification.

This function makes the naive assumption of independence between strata. Caution is therefore recommended.

Author(s)

Matt Tyers

See Also

strattest, Nstrat, rstrat, sestrat, cistrat, NChapman, NPetersen, NBailey

Examples

vstrat(n1=c(100,200), n2=c(100,500), m2=c(10,10))