rsu.sssep.rbsrg {epiR} | R Documentation |
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.
rsu.sssep.rbsrg(pstar, rr, ppr, spr, se.p, se.u)
pstar |
scalar, representing the design prevalence. |
rr |
vector, defining the relative risk values for each strata in the population. |
ppr |
vector of length |
spr |
vector of length |
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 |
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. |
## 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.