How many bugs

I learned this method from a colleague who used to work with me; Duncan Kennedy. He explained that if we both test the same functionality in our product, we can determine the probable number of bugs by comparing the ones we find. The simple formula requires that two people test independently and then compare the bugs they find. Let A be the number of bugs that the first tester found and B be the number of bugs that the second tester found. Let M be the number of bugs that are matched (same bug found by both testers). The estimated number of bugs in the feature/product under test is:

A x B ÷ M

or Person 1 bugs multiplied by Person 2 bugs divided by the number of bugs that match.

Thought tis might come in handy one day.