Sample size for demonstration of freedom (detection of disease) in a finite population



This utility calcuates the sample size required to provide a desired probability of detecting disease ( herd-sensitivity) at the specified design prevalence, for a finite population, assuming a test of known sensitivity and 100% specificity. These analyses use an approximation of the hypergeometric distribution (MacDiarmid, SC (1988). NZ Vet J, 36:39-42).

Inputs are the size of the population, test sensitivity, the desired herd-sensitivity and the design (target) prevalence.

Outputs are:

  • the number of samples required to be tested to provide the desired herd-sensitivity for the given design prevalence;
  • a table and graph of sample sizes required to provide the desired herd-sensitivity, for the specified test sensitivity and a range of population sizes and design prevalences.

Population size (for finite populations) :
Test sensitivity :
Desired herd sensitivity :
Design prevalence :


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