powPetersen {recapr}

Power for Hypothesis Testing Using the Petersen Estimator

Description

Approximates the power of a hypothesis test of the Petersen estimator by means of many simulated draws from a specified alternative distribution, conditioned on sample sizes.

Usage

powPetersen(
  nullN,
  trueN,
  n1,
  n2,
  alpha = 0.05,
  nsim = 10000,
  alternative = "less"
)

Arguments

nullN

The abundance given by the null hypothesis

trueN

The assumed abundance for the power calculation

n1

Number of individuals captured and marked in the first sample

n2

Number of individuals captured in the second sample

alpha

The alpha level for the test

nsim

Number of simulated values to draw. Defaults to 10000.

alternative

Direction of the alternative hypothesis. Allowed values are "less", "greater", or "2-sided". Defaults to "less".

Value

The approximate power of the specified hypothesis test, for the specified alternative value.

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

See Also

NPetersen, vPetersen, sePetersen, rPetersen, pPetersen, ciPetersen

Examples

powPetersen(nullN=500, trueN=400, n1=100, n2=100, nsim=1000)

Ntotry <- seq(from=250, to=450, by=25)
pows <- sapply(Ntotry, function(x)
  powPetersen(nullN=500, trueN=x, n1=100, n2=100, nsim=1000))
plot(Ntotry, pows)