HerdPlus: SeH for fixed sample size and cut-point

Input Values

Test Sensitivity:
Test Specificity:
Cut-point number of reactors:
Animal level design prevalence:
Herd-level design prevalence:
Target number of herds tested:
Target system sensitivity for optimised strategy:
Precision (significant digits):
Number of meta simulations:
Number of iterations for each meta-simulation:

NOTE:

This module may take several minutes to run, depending on numbers of iterations and simulations requested. Enter your email address and an email will be sent to you with a link to the results.

Calculate herd sensitivity (SeH) and herd specificity (SpH) for a specified test sensitivity, test specificity, cut-point number of reactors and design prevalence for a list of herd sizes and corresponding sample sizes.

A meta-simulation is also run, using the calculated SeH and SpH for each herd size, to calculate the number of herds required to be tested to achieve a specfied target system sensitivity (SSe). SSe achieved and the number of animals to be tested from a specified number of herds selected at random from the population are also calculated.

Inputs include:

  • Test sensitivity and specificity;
  • Animal-level and herd-level design prevalence values;
  • Desired cut-point number of reactors to declare a herd positive;
  • Target number of herds to be tested from population;
  • Target system sensitivity (SSe) for population testing scheme;
  • Number of iterations per simulation and number of simulations for meta-simulation of population testing;
  • The desired precision of results (number of digits to be displayed after the decimal point); and
  • Pasted data comprising columns for herd size and corresponding sample size and counts or relative frequency of each herd size in the population. Include a row of column headings in the data.

Note: Large numbers of meta-simulations generally provide only minimal additional benefit and may result in a system crash if used in combination with large numbers of iterations. A maximum of 100 meta-simulations is usually ample.

Results are calculated using the HerdPlus method (Greiner 2006?) and include:

  • Table of SeH and SpH values for each specified herd and sample size;
  • Plot of SeH and SpH values against herd size.
  • Summary table of meta-simulation results including median and 5th/95th percentiles of the numbers of herds required to achieve the target SSe and the achieved SSe and number of animals tested under the optimised scheme for the specified number of herds tested; and
  • Detailed results of meta-simulations.

Acknowledgement:

Developed by Matthias Greiner and Evan Sergeant

Paste the data to be analysed in the space below and click on submit:
1st column is herd size, 2nd column is specified sample size and 3rd column is count or relative frequency for each herd size. Include a header row of column names.

Download example herd data


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