Sample size for 2-stage risk-based surveillance, allowing for risk factors at either or both cluster and unit level

Description

Calculates sample size required (clusters and units) for a 2-stage risk-based survey with risk factors at either cluster level or unit level, or both.

Usage

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

Arguments

rr.c

relative risk values at the cluster level (vector of values, corresponding to the number of risk strata)

ppr.c

population proportions at the cluster level, corresponding to rr.c values (vector of equal length to rr.c)

spr.c

planned surveillance proportions at the cluster level, corresponding to rr.c values - the proportions of the total sample to be collected from each risk stratum (vector of equal length to rr.c).

pstar.c

cluster (herd) level design prevalence, scalar, either proportion or integer

rr.u

relative risk values at the unit level (vector of values, corresponding to the number of risk strata)

ppr.u

population proportions at the unit level, corresponding to rr.u values (vector of equal length to rr.u)

spr.u

planned surveillance proportions at the unit level, corresponding to rr.u values - the proportions of the total sample to be collected from each risk stratum (vector of equal length to rr.u).

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

Value

A list of cluster and unit level results number of clusters/units to sample per risk stratum, the total number of clusters or units per cluster to be sampled and vectors of EPI and adjusted risk values for each risk stratum.

Examples

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rr.c<- c(5,3,1)
ppr.c<- c(0.1, 0.2, 0.7)
spr.c<- c(0.4, 0.4, 0.2)
rr.u<- c(4,1)
ppr.u<- c(0.1, 0.9)
spr.u<- c(1, 0)
n.rb.2stage.2(rr.c, ppr.c, spr.c, pstar.c=0.02, rr.u, ppr.u, 
  spr.u, 0.1, se=0.9, sep.c=0.5, sep.sys=0.95) 
n.rb.2stage.2(c(3,1), c(0.2,0.8), c(0.7,0.3), pstar.c=0.05, 
  pstar.u=0.1, se=0.9, sep.c=0.95, sep.sys=0.99)

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