Calculate percent at runtime

Question

I have this problem where I have to "audit" a percent of my transtactions.

If percent is 100 I have to audit them all, if is 0 I have to skip them all and if 50% I have to review the half etc.

The problem ( or the opportunity ) is that I have to perform the check at runtime.

What I tried was:

audit = 100/percent 

So if percent is 50

audit = 100 / 50 ( which is 2 ) 

So I have to audit 1 and skip 1 audit 1 and skip 1 ..

If is 30

audit = 100 / 30 ( 3.3 )

I audit 2 and skip the third.

Question

I'm having problems with numbers beyond 50% ( like 75% ) because it gives me 1.333, ...

When would be the correct algorithm to know how many to audit as they go?... I also have problems with 0 ( due to division by 0 :P ) but I have fixed that already, and with 100 etc.

Any suggestion is greatly appreciated.

Answer 1

Why not do it randomly. For each transaction, pick a random number between 0 and 100. If that number is less than your "percent", then audit the transaction. If the number is greater than your "percent", then don't. I don't know if this satisfies your requirements, but over an extended period of time, you will have the right percentage audited.

If you need an exact "skip 2, audit one, skip 2 audit one" type of algorithm, you'll likely have luck adapting a line-drawing algorithm.