4. Three tests idea to increase registration
Test Idea 3: Revamp the course
pages
Test Idea 1: Preload sign-up
modal on our learning platform
Test Idea 2: Add recommended
courses to top of search page
6. Prioritizing: Estimate number of new conversion per day
What’s the population of your test idea?
What’s the current conversion rate?
What’s your estimated increase?
Then: Multiply to get new daily conversions
11. Calculating Impact
Page Visitors per Day Conversion Rate Estimated Impact New Conversions
per Day
Learning Platform 70,000 2% 5% 70
Search page 10,000 21% 2% 42
Course page 40,000 10% 3% 120
VD x CR EIx = NCD
12. Picking one test
Page Visitors per Day Conversion Rate Estimated Impact New Conversions
per Day
Homepage 70,000 2% 5% 70
Pricing page 10,000 21% 2% 42
Course page 40,000 10% 3% 120
VD x CR EIx = NCD
14. Creating: Run a Power Analysis
• 80% Power: if there’s an effect of this size, there’s an 80% chance
you will detect it
• How long will you need to run your experiment for to get 80%
power?
16. Deciding on changes to try
What could
improve
registration on
the course page?
Add registration form on page?
Add user testimonials?
Preload registration modal?
Add company logos?
Add video?
Why not all of them!
17. … Two Months Later
Oh no, we spent two
months working and
registrations didn’t go
up! Why didn’t it
work?
Data Scientist:
22. Run it and dump the data on the data scientist?
We finished the
experiment! Can you
analyze it for us?
“To consult the statistician after
an experiment is finished is often
merely to ask [them] to conduct a
post mortem examination.
[They] can perhaps say what the
experiment died of.”
- Sir R.A. Fisher
23. Creating: Have a Data Scientist Involved
• Can make sure you’re tracking the right metrics
• Can help with the power calculation
• Can help iterate on ideas
25. Things that have happened
➔ People are put in both control and treatment
➔ People in the experiment have no page views
➔ People have multiple experiment starts in the same group
➔ Experiment starts didn’t have cookies (so we couldn’t track user)
➔ People weren’t split evenly between control and treatment
31. Decision-Making: Be careful of launching on “neutral”
• What is the technical complexity and debt you’re adding?
• Is it a foundational feature?
• Could be a negative impact too small to detect
• Decide beforehand whether you’ll launch it on “neutral”
34. Research papers
➔ Controlled experiments on the web: survey and practical guide (2008)
➔ Seven rules of thumb for web site experiments (2014)
➔ A dirty dozen: twelve common metric interpretation pitfalls in online
controlled experiments (2017)
➔ Democratizing online controlled experiments at Booking.com (2017)
35. Blog posts and presentations
➔ Design for Continuous Experimentation by Dan McKinley
➔ Scaling Airbnb’s Experimentation Platform by Jonathan Parks
➔ Please, please don’t A/B test that by Tal Raviv
➔ How Etsy handles peeking in A/B Testing by Callie McRee and
Kelly Shen