Audit Random Sample Size

Hi all

I’m having some difficulty with some sampling work. I’ve searched around for a few days but need a little help. Hopefully someone here will be able to point me in the right direction.

The purpose of the sampling is to audit claims that have been entered and to measure the percentage of claims that have an input error, I will be using a 95% CL and 5% CI.

I want to base my sample on the input error rate I estimate to be at 20%. The total number of claims input each month will be between 250 and 350.

I would like to be sensitive to the estimated error rate and population size as well as the CL and CI.

The closest calculator I could find for this is shown here: (useful because I can view the formulas in the source). But I’m not completely sure if this an appropriate method?

I also saw the Slovin formula mentioned here that wouldn’t take into account my estimated input error rate.

Any help is greatly appreciated.

Many thanks