Chapter 22: An Illustrated Guide to Web Experiments

Editor's Note: Experimentation is an essential conversion rate optimization (CRO) activity. However, the statistics that form the foundation of running web experiments can intimidate inbound marketers who are new to CRO. The author created this illustrated guide to conducting web experiments with this in mind. It was originally published March 26, 2012, on The Moz Blog.

Web experimentation is a great methodology to improve most things on the web. It can be used to make adjustments to existing products such as increasing user engagement and conversion rate. But it can also be used to guide entire business decisions, as suggested by Eric Ries ( The primary strength of controlled web experiments is the possibility to isolate variables, and thus examine causality between different metrics such as tagline and conversion rate (see

Much of the literature on experimental design has its roots in statistics and can be quite intimidating. To make it more accessible, I created this illustrated guide to web experiments.

Author's Note: Special thanks to Andreas Høgenhaven, who kindly made the illustrations for this guide.

Before getting started on the experiment, you need to get the basics right: Test metrics that align with your long-term business goals (see ...

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