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Herd-level sensitivity for testing in a finite population


This utility estimates the probability of detecting disease (herd-sensitivity) in a finite population, if it is present at the specified design prevalence, assuming a test of known sensitivity and 100% specificity and that all samples have a negative test result. These analyses use an approximation of the hypergeometric distribution (MacDiarmid, SC (1988). NZ Vet J, 36:39-42). Because test specificity is assumed to be 100%, herd-specificity for these calculations is also 100%.

Inputs are:

  • Sample size tested;
  • Size of the population;
  • Test sensitivity; and;
  • Design (target) prevalence.

Outputs are:

  • The herd-level sensitivity for the given sample size, population size, test sensitivity and design prevalence; and
  • A table of herd-sensitivity values for a range of design prevalence and sample size values for the specified population size.