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%.