HerdPlus utilities

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

Test sensitivity

Test specificity

Maximum herd sensitivity

Minimum herd specificity

Animal level design prevalence

Herd size

Sample size range:

From

To

Cut-point range:

From

To

Precision (significant digits)

Submit

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.

Acknowledgement

Developed by Matthias Greiner and Evan Sergeant