SS.est.Ratio | R Documentation |

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()

```
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.

`Sight.Est`

, `Wong.est`

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