HerdPlus: SeH and SpH for varying sample sizes

Input Values

Test Sensitivity:
Test Specificity:
Animal level design prevalence:
Herd Size:
Cut-point number of reactors:
Precision (significant digits):

Calculate SeH and SpH for a range of sample sizes, for specified test sensitivity, test specificity, herd size and cut-point number of reactors. Values are calculated for all sample sizes from the cut-point number of reactors up to the specified herd size.

Inputs include:

  • Test sensitivity and specificity;
  • Animal-level design prevalence (the hypothetical prevalence to be detected);
  • Herd size;
  • The cut-point number of reactors to classify a herd/flock as positive (if there are fewer reactors than the specified cut-point the herd is negative, if the number of reactors is >= cut-point 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.

Tables and plots are presented for SeH and SpH for four different estimation methods:

  1. Simulated sampling using the specified number of iterations;
  2. HerdPlus: Using the hypergeometric distribution. Greiner et al, manuscript in preparation;
  3. HerdAcc: Jordan D, McEwen SA, 1998. Herd-level test performance based on uncertain estimates of individual test performance, individual true prevalence and herd true prevalence. Prev. Vet. Med. 3: 187-209; and
  4. FreeCalc: Cameron AR, Baldock FC, 1998. A new probability formula for surveys to substantiate freedom from disease. Prev. Vet. Med. 34: 1-17


Developed by Matthias Greiner and Evan Sergeant


  Home  |   About this site  |   Glossary   |   References   |   Links   |  271 recent calculations

This site was created by Ausvet with funding from a range of sources.
It provides a range of epidemiological tools for the use of researchers and epidemiologists, particularly in animal health.
Please send any comments, questions or suggestions to Evan Sergeant
© 2018 Ausvet