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HerdPlus utilities

HerdPlus: SeH and SpH for range of sample sizes and cut-points for given herd size

Sample size range:

Cut-point range:

Calculate herd sensitivity (SeH) and herd specificity (SpH) for a range of sample sizes and cut-point numbers of reactors, for specified herd size, test sensitivity, test specificity and design prevalence. Also calculates:

  • SeH values where SpH is constrained to be greater than a specified minimum value; and
  • The sample size and cut-point for maximum SeH given constraints of the range of sample sizes and cut-points and specified minimum SpH and maximum SeH.

Inputs include:

  • Test sensitivity and specificity;
  • Animal-level design prevalence (the hypothetical prevalence to be detected);
  • Maximum desired SeH and minimum SpH;
  • Specified herd/population size;
  • Maximum and minimum sample sizes to be considered;
  • Maximum and minimum cut-point number of reactors to classify a herd/flock as positive; and
  • The desired precision of results (number of digits to be displayed after the decimal point).

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

  • Tables and plots of SeH and SpH for combinations of sample size and cut-points;
  • A table of SeH values corresponding to SpH values greater than or equal to the specified minimum SpH; and
  • A summary of the sample size, cut-point and maximised SeH given the specified constraints on SeH and SpH.


Developed by Matthias Greiner and Evan Sergeant