Wong.est: Sightability estimate with variance components estimator from...

In SightabilityModel: Wildlife Sightability Modeling

Sightability estimate with variance components estimator from Wong (1996)

Description

Estimates population size, with variance estimated using Wong's (1996) estimator. This function will usually be called by Sight.Est function (but see details).

Usage

Wong.est(
  total,
  srates,
  nh,
  Nh,
  stratum,
  subunit,
  covars,
  beta,
  varbeta,
  smat = NULL
)

Arguments

total	Number of animals in each independently sighted group
srates	Vector of plot-level sampling probabilities (same dimension as total).
nh	Number of sample plots in each stratum
Nh	Number of population plots in each stratum
stratum	Stratum identifiers (associated with the independently observed animal groups)
subunit	Plot ID (associated with the independently observed animal groups)
covars	Matrix of sightability covariates (associated with the independently observed animal groups)
beta	Logistic regression parameter estimates (from fitted sightability model)
varbeta	Estimated variance-covariance matrix for the logistic regression parameter estimates (from fitted sightability model)
smat	Estimated variance-covariance matrix for the inflation factors (1/probability of detection). This is an n.animal x n.animal matrix, and is usually calculated within the Wong.est function. Non-null values can be passed to the function (e.g., if a bootstrap is used to estimate uncertainty due to the estimated detection parameters).

Details

This function is called by Sight.Est, but may also be called directly by the user (e.g., in cases where the original sightability [test trial] data are not available, but the parameters and var/cov matrix from the logistic regression model is available in the literature).

Value

tau.hat	Sightability estimate of population size, tau^
VarTot	Estimated variance of tau^
VarSamp	Estimated variance component due to sampling aerial units
VarSight	Estimated variance component due to sighting process (i.e., series of binomial rv for each animal group)
VarMod	Estimated variance component due to estimating detection probabilities using test trial data

Author(s)

John Fieberg

References

Rice CG, Jenkins KJ, Chang WY (2009). Sightability Model for Mountain Goats." The Journal of Wildlife Management, 73(3), 468- 478.

Steinhorst, R. K., and M.D. Samuel. (1989). Sightability adjustment methods for aerial surveys of wildlife populations. Biometrics 45:415-425.

Wong, C. (1996). Population size estimation using the modified Horvitz-Thompson estimator with estimated sighting probabilities. Dissertation, Colorado State University, Fort Collins, USA.

See Also

Sight.Est, SS.est

SightabilityModel documentation built on Aug. 20, 2023, 1:08 a.m.