[yummyfajitas]

We are using a lower standard of evidence than medical decisions. The goal is to get as many clicks/conversions as possible in aggregate, most of the time. I.e., if you have a call to action ("3 day sale", "spring sale", "march sale") that dies in 3 days, we'll do the best we can to increase your conversions in those 3 days.

Similarly, if you have 10,000 seo-optimized microsites, each with traffic too low for a per-site A/B test, we'll improve your conversion rate across the 10,000 microsites.

If you want to make a long term change (e.g., logo, button color, feature) for a high traffic site (your one and only landing page) you are better off using a traditional A/B test.