rsu.sspfree.rs {epiR} | R Documentation |
Calculates the required sample size to achieve a desired (posterior) probability of disease freedom assuming representative sampling, imperfect test sensitivity and perfect test specificity.
rsu.sspfree.rs(N = NA, prior, p.intro, pstar, pfree, se.u)
N |
scalar integer or vector of integers the same length as |
prior |
scalar probability (0 to 1), representing the prior probability that the population is free of disease. |
p.intro |
scalar or vector of the same length as |
pstar |
scalar numeric or vector of numbers the same length as |
pfree |
scalar numeric or vector of numbers the same length as |
se.u |
scalar (0 to 1) representing the sensitivity of the diagnostic test at the surveillance unit level. |
A list comprised of three elements:
n |
a vector listing the required sample sizes. |
sep |
a vector listing the population sensitivity estimates. |
adj.prior |
a vector listing the adjusted priors. |
This function returns the sample size to achieve a desired (posterior) probability of disease freedom. Function rsu.sssep.rs
returns the sample size to achieve a desired surveillance system sensitivity.
Martin P, Cameron A, Greiner M (2007). Demonstrating freedom from disease using multiple complex data sources 1: A new methodology based on scenario trees. Preventive Veterinary Medicine 79: 71 - 97.
Martin P, Cameron A, Barfod K, Sergeant E, Greiner M (2007). Demonstrating freedom from disease using multiple complex data sources 2: Case study - Classical swine fever in Denmark. Preventive Veterinary Medicine 79: 98 - 115.
## EXAMPLE 1: ## Prior surveillance activities and expert opinion lead you to believe that ## there's a 75% chance that your country is free of disease X. To confirm ## your country's disease freedom status you intend to use a test at the herd ## level which has a diagnostic sensitivity of 0.95. The probability of ## disease introduction during the time period of interest is relatively ## low, say 0.01. How many herds need to be sampled to be 95% confident ## that the country is free of disease X assuming a design prevalence of ## 0.01? rsu.sspfree.rs(N = NA, prior = 0.75, p.intro = 0.01, pstar = 0.01, pfree = 0.95, se.u = 0.95) ## A total of 198 herds need to be sampled to meet the requirements of the ## study.