Best Practices & Lessons Learned from 30,000 A/B and Multivariate Tests – summary of Optimizely’s video

Optimizely’s Best Practices & Lessons Learned from 30,000 A/B and Multivariate Tests video is an advert for A/B testing in general, and for Optimizely Optimizely as a tool for running and creating tests.

This video features some useful examples of multivariate tests done during the Obama campaign. Here’s my summary:

  1. Nothing is sacred. Question assumptions
  2. Explore before you refine
  3. Less is more
    Some content experiments: – One Kings Lane: Removing 2 fields led to an 8.4% increase in signups
    – Clinton Bush Haiti Fund: Removing title field and phone number field saw an 10.9% increase in the $value of each visitor’s donation
    – AVG Australia: Removing links from the checkout process increased the $ value of each visitor by 16.8%
  4. Words matter. Focus on your call to action.
    – Donate Now, Please Donate, Why Donate?, Donate and Get a Gift, Contribute: which is better? The status of the individual makes a difference to which of these options is most effective: new people respond best to “Donate and Get a Gift” (+15.2% $ per pageview compared to Donate Now); people who have signed up but never donated responded best to “Please Donate” (+27.8%), and people who have previously donated responded best to “Contribute” (+18.4%)
    – Clinton Bush Haiti Fund’s donate form – changing the confirmation button from “Submit” to “Support Haiti” increased $ per visitor by 15.75%.
  5. Fail Fast
    You can get statistically significant results very quickly.
  6. Start Today
  • Q: How many variations should you test at once?
    Tradeoff between breadth of test and speed of reaching statistical significance.
    A good starting point is to test with 4 variations, then take the top 2 and test them again.
  • Q: What percentage of website traffic should you allocate to a test?
    You can control this per experiment.
    They recommend allocating as much as you can, to reach statistical significance sooner.
  • Q: Can you target specific types of visitors?
    You can choose to target all, new, or returning visitors.
  • Q: How do you target paid traffic?
    Do this with the targeting interface: trigger by origin location, or match certain query parameters (eg utm_source)
  • Q: How do you test dynamic pages?
    Go to interactive mode to make the dynamic stuff happen.
    Tell us when you want to activate optimizely. By default it loads on page load; but you can activate it manually through the API.
  • Q: Does Optimizely work for pages behind logins or paywalls?
    Yes, as long as you’ve added the snippet to the page.
  • Q: How do you test big changes to a page, or test a new page against an old one?
    If you want to test a big change to a page, or test against an old page, you can make it so that visitors selected for a specific variation are redirected to another URL. (Make sure that the snippet is on both pages)
  • Q: How do you test server-side changes? i.e. where the variations are reflected on the backend and not just on the front end (eg graphics). Eg price variations.
    A: Optimizely wants to improve at this. Most people doing this currently set up two different pages, and set up a javascript gate on the front end to pass 50% of visitors to one page, the other 50% go to the other.
    See and
  • Q: How soon to pull the plug on a variation when it looks like it’s not performing well?
    A: Wait until you get statistical significance. The early days of at test may not be truly representative.