Traps to avoid in A/B testing.
Don’t end a test too early.
You need a lot of people in your A/B tests to determine which one is a winner. If you chose a route where there is not a substantial improvement, it could be the worse alternative—and your wonderful testing mechanism just failed you.
Use an online calculator (Optimizely has one) to determine your sample size. Instead of letting your test run for a set amount of time, focus on the number of samples collected.
Run for a (likely) maximum of 4 weeks. After four weeks, cookies begin to be reset and users will start being counted.
If you have enough traffic, you could consider splitting that traffic into segments and running each segment for 4 weeks.
Test things that matter.
While color tweaks or whether or not to round button is interesting—will it actually make a difference in your conversion rate?
If your call to action button’s contrast is poor against the rest of the website, then fixing it will help. If the rest of the website has styling that is smooth and rounded, then making your button’s corners rounded might help.
But, just changing this to change it will likely yield no perceivable changes. Or, based on previous notes, you are free to stop the test wherever it provides the most positive outlook to furthering your career as nothing substantial will be gained.
Have proper expectations.
Booking.com constantly runs A/B tests. You might say they are experts. They have 75 product teams working on tests. Every 10-12 months the teams are completely rebuilt so that everyone stays fresh with new ideas.
Their success rate for A/B tests is 10%. Get that.
Granted, they have a mature A/B testing system and have already dealt with the low-hanging fruit.
Is a 10% success rate too small for you? If the alternative is 0% success rate (by not trying), you have to agree that 10% is better than nothing. Remember that these successes compound. Two successes = 21% improvement (better than 2 x 10%).
What if I don’t have enough traffic to run A/B tests?
User interviews are your answer. You should be doing this whether or not A/B tests make sense. Talk to customers. Hear what they have to say. Watch them navigate your website.