Description Usage Arguments Value Author(s) References See Also

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()

1 2 3 4 5 6 7 8 9 10 11 12 13 | ```
SS.est.Ratio(
numerator,
denominator,
srates,
nh,
Nh,
stratum,
subunit,
covars,
beta,
varbeta,
smat = NULL
)
``` |

`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). |

`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 |

Carl James Schwarz, cschwarz.stat.sfu.ca@gmail.com

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.

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