This calculator is intended to help design surveys to estimate Herd Level Prevalence when the individual test is imperfect (1).
This calculator runs both of these stages together to allow you to see the effect of adjusting parameters on the sampling at both stages. You may realise that there is no “single answer” because there is usually a trade-off between the number of animals to test and the number of herds.
We hope the value of the calculator is to allow the user to “experiment” with different values in order to focus in on their own preferred design whilst recognising the impact of those values on the predicted performance of the survey.
The calculator is controlled using the inputs on the left-hand side of the Graphical Output page. The following parameters can be adjusted
The results are expressed as the number of animals needing tested plotted against the number of herds. A range of values for tolerance and herd sensitivity are given. For more information, hover over the individual points.
This two-stage sample size calculator was built by Andrew Duncan. If you have any comments or suggestions about improvements that can be made please get in touch. If you are interested in developing this further, the code is currently hosted on Github.
This was funded by the Scottish Government within the RESAS WP6.5 knowledge transfer programme.