I just found out about this very cool, free online testing tool. It's call Split Tester and it will help you predict if your early split test results are reliable. That is, will they hold up over the long run? This is great because it allows you to test for a shorter period of time, which can save you money, yet still get results that are reliable.
You can use this to help you make decisions with your Google Adwords ads, or landing page copy, because it measures conversion rates.
All you need to test your results are your total number of clicks and your clickthrough percentage rate. Google Adwords gives you both. You enter both sets of these numbers for the two different ads you are testing to find out if your split test results are reliable.
I have used this recently to help me make some pricing decisions on a new product and this tool has helped me make those decisions faster than I could have otherwise. And the sooner I finish testing my pricing, the sooner I can start offering this new product for sale to the masses. So in this case, time absolutely is money!
If you're not yet using Google Adwords, and you'd like to learn how, I highly recommend Perry Marshall's book, A Definitive Guide to Google Adwords. It's inexpensive and very comprehensive and easy to read. Plus, Perry Marshall has a free, five-day ecourse that is also very helpful.