Livestock Disease Surveys: A Field Manual for Veterinarians

0.90 proportion positive abattoir surveillance animal sampled binomial distribution brucellosis CHANCES OF DETECTING Cluster sampling confidence interval confidence level desired confidence of detecting detect any positives detecting at least Detecting the Presence disease is present Disease Prevalence Epidemiology estimate Example Expected proportion false negative false positive finite population found clean n/N gives the width herds or flocks hypergeometric distribution large population least one positive level of occurrence LIMITS FOR NUMBER Livestock Disease Surveys Manual for Veterinarians microbial culture Monitoring Multistage Sampling number of animals number of females number of positives number sampled period prevalence point prevalence population given population TABLE positive result positives is 28 predictive value prevalence of disease proportion negative proportion of positives ratio sample size required select a random sensitivity and specificity sheep simple random sample specified proportion stratified sample Systematic sampling table gives test to give total population two-digit random numbers upper limit width of confidence