1-Stage Freedom analysis

Use these utilities to assist with planing and analysis of simple 1-stage surveys to demonstrate disease freedom. Methods are appropriate for sampling units (animals, fish, plants, etc) to demonstrate cluster (herd, flock, farm, tank, etc) freedom, or for either individuals or clusters to demonstrate population freedom. All methods assume representative sampling of units from the population and methods are included for large (or unknown) and finite (known) population size. Most of the options (except where noted) assume perfect (100%) test specificity.

If you prefer the old menu click here.

Click here for Some important formulae for freedom analyses.


Assuming perfect test specificity (100%)

Sample size calculation

Use these options to estimate required sample size assuming perfect test specificity:

Population sensitivity calculation (SeH or SSe)

Use these options to calculate cluster or population-level sensitivity assuming perfect test specificity:

Allowing for imperfect test specificity (<100%)

Sample size calculation

Use these options to estimate required sample size assuming imperfect test specificity:

Population sensitivity with imperfect test specificity

Use these options to calculate cluster or population-level sensitivity assuming imperfect test specificity:

Some other useful options

Design prevalence

Confidence of population freedom from disease


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This site was created by Ausvet with funding from a range of sources.
It provides a range of epidemiological tools for the use of researchers and epidemiologists, particularly in animal health.
Please send any comments, questions or suggestions to Evan Sergeant
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