rsu.sssep.rbsrg {epiR} R Documentation

## Sample size to achieve a desired surveillance system sensitivity assuming risk-based sampling and a single sensitivity value for each risk group

### Description

Sample the size to achieve a desired population sensitivity assuming risk-based sampling, a single sensitivity value for each risk group and perfect test specificity.

### Usage

```rsu.sssep.rbsrg(pstar, rr, ppr, spr, se.p, se.u)
```

### Arguments

 `pstar` scalar, representing the design prevalence. `rr` vector, defining the relative risk values for each strata in the population. `ppr` vector of length `rr`, defining the population proportions in each strata. `spr` vector of length `rr` representing the planned surveillance proportion for each strata in the population. `se.p` scalar (0 to 1) representing the desired surveillance system (population-level) sensitivity. `se.u` scalar (0 to 1) or vector of the same lengthe as `rr` representing the sensitivity of the diagnostic test applied at the unit level.

### Value

A list of comprised of four elements:

 `n` a vector listing the required sample sizes for each (risk) strata. `total` scalar, representing the total sample size. `epinf` a vector listing the effective probability of infection estimates. `adj.risk` a vector listing the adjusted risk estimates.

### Examples

```## EXAMPLE 1:
## A cross-sectional study is to be carried out to confirm the absence of
## disease using risk based sampling. Assume a population level design
## prevalence of 0.10 and there are 'high', 'medium' and 'low' risk areas
## where the risk of disease in the high risk area compared with the low risk
## area is 5 and the risk of disease in the medium risk area compared with
## the low risk area is 3. The proportions of the population at risk in the
## high, medium and low risk area are 0.10, 0.10 and 0.80, respectively.
## Half of your samples will be taken from individuals in the high risk area,
# 0.30 from the medium risk area and 0.20 from the low risk area. You intend
## to use a test with diagnostic sensitivity of 0.90 and you'd like to take
## sufficient samples to return a population sensitivity of 0.95. How many
## units need to be sampled to meet the requirements of the study?

rsu.sssep.rbsrg(pstar = 0.10, rr = c(5,3,1), ppr = c(0.10,0.10,0.80),
spr = c(0.50,0.30,0.20), se.p = 0.95, se.u = 0.90)

## A total of 14 units needs to be sampled to meet the requirements of the
## study: 7 from the high risk area, 5 from the medium risk area and 2 from
## the low risk area.
```

[Package epiR version 2.0.38 Index]