Without a basic understanding of statistics, you can often present misleading results to your clients or superiors. This can lead to underwhelming results when you roll out new versions of a page which on paper look like they should perform much better. In this post I want to cover the main aspects of planning, monitoring and interpreting CRO results so that when you do roll out new versions of pages, the results are much closer to what you would expect. I’ve also got a free tool to give away at the end, which does most of this for you.Planning
A large part running a successful conversion optimisation campaign starts before a single visitor reaches the site. Before starting a CRO test it’s important to have:A hypothesis of what you expect to happenAn estimate of how long the test should takeAnalytics set up correctly so that you can measure the effect of the change accurately
Assuming you have a hypothesis, let’s look at predicting how long a test should take.How long will it take?
As a general rule, the less traffic that your site gets and/or the lower the existing conversion rate, the longer it will take to get statistically significant results. There’s a great tool by Evan Miller that I recommend using before starting any CRO project. Entering the baseline conversion rate and the minimum detectable effect (i.e. What is the minimum percentage change in conversion rate that you care about, 2%? 5%? 20%?) you can get an estimate of how much traffic you’ll need to send to each version. Working backwards from the traffic your site normally gets, you can estimate how long your test is likely to take. When you arrive on the site, you’ll see the following defaults: