sample size...help

[bluepenink]

hello

im having to do an audit for a contest for our team that qualified.

i have approx 18 ppl...i have to audit their invoices that make up their total claimed revenue.

however the issue is....there are over 800 invoices per person, and it's only me doing the audit. im not auditor, however i was wondering if someone can pls help me determine a "threshold" as to how i can determine a sample size?

the invoices vary from $40-$1200 (max)....., so what would be a good amount to look at i.e. invoice less than $80 are immaterial, so anything greater than $80 i should audit.....does anyone have any suggestions??

pls help thx u so much

 

[Stacko]

This sort of thing goes on all the time in Financial Services, for example detecting internet fraud transactions.

Basically you weight your items and then work down from the highest rated items until you run out of time.

In your case you can weight on value - start with the $1200s and work down. You may also want to add other factors.

There is no formula for sample size.

If you post further on this, please say how Excel is involved.