title: Is it possible to do A/B testing by page rather than by individual?
body: <p>Lets say I have a simple ecommerce site that sells 100 different t-shirt designs.  I want to do some a/b testing to optimise my sales.  Let's say I want to test two different "buy" buttons.  Normally, I would use AB testing to randomly assign each visitor to see button A or button B (and try to ensure that that the user experience is consistent by storing that assignment in session, cookies etc).</p>
  
  <p>Would it be possible to take a different approach and instead, randomly assign each of my 100 designs to use button A or B, and measure the conversion rate as <strong>(number of sales of design n) / (pageviews of design n)</strong></p>
  
  <p>This approach would seem to have some advantages; I would not have to worry about keeping the user experience consistent - a given page (e.g. www.example.com/viewdesign?id=6) would always return the same html.  If I were to test different prices, it would be far less distressing to the user to see different prices for different designs than different prices for the <em>same</em> design on different computers.  I also wonder whether it might be better for SEO - my suspicion is that Google would "prefer" that it always sees the same html when crawling a page.</p>
  
  <p>Obviously this approach would only be suitable for a limited number of sites; I was just wondering if anyone has tried it? </p>