Input Values 

This utility calculates the sample size required to achieve a target population or cluster level sensitivity for a survey.
For these calculations unit specificity is assumed to be 100%.
For cluster (herd, flock, etc) level calculations, enter test sensitivity, unitlevel design prevalence and
required clusterlevel sensitivity. Alternatively,
for population level calculations enter clusterlevel (herd) sensitivity, clusterlevel design prevalence and required populationlevel sensitivity.
Calculations use the hypergeometric approximation if population size is provided, or binomial method if population size is not specified.
Inputs are:
 Design prevalence as either a proportion or an integer number of units (animals for cluster level sensitivity and clusters for populationlevel sensitivity);
 Unit sensitivity (test sensitivity to calculate cluster (herd) sensitivity or cluster (herd) sensitivity tocalculate population sensitivit;
 Required populationlevel sensitivity; and
 Population size (optional if design prevalence is specified as a proportion, required if design prevalence is a number of units). Leave population size blank if not known.
Outputs are:
 Required sample size for the given target population sensitivity, design prevalence and unit sensitivity; and
 A table and graph of sample sizes for varying population and design prevalence values
and the given target population sensitivity and unit sensitivity.
