[marksbren]

Good find. Here is a summary for those who don't want to dig though the Scribd document.

Here are the two versions: http://dl.dropbox.com/u/493143/ABTest.png (A = Old Page, B = New Page)

1. Doctor FootCare updated their checkout page to include a coupon code field (and a few other minor changes)

2. With the updated version, Doctor FootCare saw a 90% decrease in revenue.

3. Once Doctor FootCare took the coupon code out of the new version (B) the conversion rate of the page was 6.5% higher than the old checkout page (A). The new page without the coupon code field is not pictured.

That is a huge change, but I would not blindly assume that this result proves that the coupon code field should not be included in your checkout form. I would also like more data about the test.