

Calculate herdsensitivity and herdspecificity for a given herd size,
test sensitivity, test specificity, sample size and
cutpoint number of reactors.
Inputs include:
 Test sensitivity and specificity;
 Animallevel design prevalence (the hypothetical prevalence to be detected);
 Size of the herd or flock being sampled;
 Number of individuals tested;
 The cutpoint number of reactors to classify a herd/flock as positive
(if there are fewer reactors than the specified cutpoint the herd is negative,
if the number of reactors is >= cutpoint the herd is positive);
 The desired precision of results (number of digits to be displayed after the decimal point); and
 The number of iterations for the simulation method.
Results are presented for four different estimation methods:
 Simulated sampling using the specified number of iterations;
 HerdPlus: Using the hypergeometric distribution. Greiner et al, manuscript in preparation;
 HerdAcc: Jordan D, McEwen SA, 1998. Herdlevel test performance
based on uncertain estimates of individual test performance, individual true
prevalence and herd true prevalence. Prev. Vet. Med. 3: 187209; and
 FreeCalc: Cameron AR, Baldock FC, 1998. A new probability formula
for surveys to substantiate freedom from disease. Prev. Vet. Med. 34: 117
Acknowledgement:Developed by Matthias Greiner and Evan Sergeant
