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Sample Size Calculations for Surveys to Substantiate Freedom of Populations from Infectious Agents
Author(s) -
Johnson Wesley O.,
Su ChunLung,
Gardner Ian A.,
Christensen Ronald
Publication year - 2004
Publication title -
biometrics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.298
H-Index - 130
eISSN - 1541-0420
pISSN - 0006-341X
DOI - 10.1111/j.0006-341x.2004.00143.x
Subject(s) - sample size determination , frequentist inference , hypergeometric distribution , statistics , mathematics , null hypothesis , bayesian probability , population , infectious disease (medical specialty) , sampling (signal processing) , binomial (polynomial) , medicine , disease , computer science , bayesian inference , pathology , environmental health , filter (signal processing) , computer vision
We develop a Bayesian approach to sample size computations for surveys designed to provide evidence of freedom from a disease or from an infectious agent. A population is considered "disease-free" when the prevalence or probability of disease is less than some threshold value. Prior distributions are specified for diagnostic test sensitivity and specificity and we test the null hypothesis that the prevalence is below the threshold. Sample size computations are developed using hypergeometric sampling for finite populations and binomial sampling for infinite populations. A normal approximation is also developed. Our procedures are compared with the frequentist methods of Cameron and Baldock (1998a, Preventive Veterinary Medicine34, 1-17.) using an example of foot-and-mouth disease. User-friendly programs for sample size calculation and analysis of survey data are available at http://www.epi.ucdavis.edu/diagnostictests/.