[btilly]

See https://news.ycombinator.com/item?id=12541290 for one rule of thumb and methodology.

My experience is that most tests will come out under 5% differences. But most organizations will have some test that they could run with a greater than 15% win.

If your business scale does not allow you to run tests and detect the wins you hope for, you're better off following other people's best practices than you are trying to discover best practices from running your own tests.

Also note that most businesses have a "conversion funnel" where there are a number of steps from visitor to getting paid. If your business is big enough, you want to focus on getting paid. If your business is too small to get results that way, you should get started with just the first step in the funnel. That's what Patrick did with the trial signup form.