# Design prevalence required to achieve target population (cluster or system) sensitivity

Calculate the design prevalence required to achieve a desired cluster or system (population) level sensitivity.

Inputs are the test or cluster sensitivity for the sampling, sample size tested, population size (optional) and the required cluster or system sensitivity. Enter test sensitivity if the target is a cluster level sensitivity or cluster-sensitivity if the target is a system or population level sensitivity. If population size is entered the hypergeometric approximation is used, otherwise the calculation is based on the binomial distribution.

The main output is the design prevalence required to achieve the specified target cluster or system sensitivity. This design prevalence is a unit-level prevalence for a target cluster sensitivity, or a cluster level prevalence for a target system (population) level sensitivity.

If the size of the population is provided, an additional output is the expected maximum number of infected units in the population, for the given confidence level (population sensitivity) and assuming that all samples tested are negative.