

Calculate herd sensitivity for a range of
design prevalence values, for specified test sensitivity,
test specificity, herd size, sample size and
cutpoint number of reactors. SeH is calculated for prevalence values ranging from 0.005 to 0.2
Inputs include:
 Test sensitivity and specificity;
 Herd size;
 Sample size 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.
Table and plot of SeH 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
