SS.est.Ratio {SightabilityModel}

Sightability estimate or ratio with variance components estimator from Steinhorst and Samuel (1989) and Samuel et al. (1992). This is merely a stub and has not been implemented.

Description

Estimates ratio, with variance estimated using Steinhorst and Samuel (1989) and Samuel et al.'s (1992) estimator. Usually, this function will be called by Sight.Est.Ratio()

Usage

SS.est.Ratio(
  numerator,
  denominator,
  srates,
  nh,
  Nh,
  stratum,
  subunit,
  covars,
  beta,
  varbeta,
  smat = NULL
)

Arguments

numerator, denominator

Number of animals for the numerator and denominator of the ratio in each independently sighted group

srates

Plot-level sampling probability

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 SS.est.Ratio 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).

Value

ratio.hat

Sightability estimate of ratio, ratio^

VarRatio

Estimated variance of ratio^

VarSamp, VarSight, VarMod

Estimated variance component due to sampling, sightability and model set to NA

Author(s)

Carl James Schwarz, [e-mail]

References

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, Wong.est