Description Usage Arguments Value Examples

Calculates sample size required (clusters and units) for a 2-stage risk-based survey with a single risk factor at the cluster level only.

1 2 | ```
n.rb.2stage.1(rr, ppr, spr, pstar.c, pstar.u, se = 1, sep.c = 0.95,
sep.sys = 0.95)
``` |

`rr` |
relative risk values (vector of values, corresponding to the number of risk strata) |

`ppr` |
population proportions corresponding to rr values (vector of equal length to rr) |

`spr` |
planned surveillance proportions corresponding to rr values - the proportions of the total sample to be collected from each risk stratum (vector of equal length to rr). |

`pstar.c` |
cluster (herd) level design prevalence, scalar, either proportion or integer |

`pstar.u` |
unit (animal) level design prevalence, scalar, either proportion or integer |

`se` |
unit sensitivity of test (proportion), scalar, default = 1 |

`sep.c` |
desired cluster-level sensitivity (proportion), scalar, default = 0.95 |

`sep.sys` |
desired population-level sensitivity (proportion), scalar, default = 0.95 |

A list of seven elements: 1) a vector (of the same length as rr) of the numbers of clusters to sample from each risk stratum, 2) the total number of clusters to be sampled, 3) a vector of EPI values for each risk stratum, 4) a vector of adjusted risk values for each risk stratum, 5) the number of untis to be sampled per cluster 6) a vector of the total numbers of units to be sampled for each risk stratum 7) the overall total number of units to be sampled

1 2 3 4 5 |

```
$n
[1] 79 79 39
$total
[1] 197
$epi
[1] 0.027777778 0.016666667 0.005555556
$adj.risk
[1] 2.7777778 1.6666667 0.5555556
$units
[1] 18
$risk.units
[1] 1422 1422 702
$total.units
[1] 3546
$n
[1] 39 16
$total
[1] 55
$epi
[1] 0.10714286 0.03571429
$adj.risk
[1] 2.1428571 0.7142857
$units
[1] 32
$risk.units
[1] 1248 512
$total.units
[1] 1760
```

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