Finally, I will talk about how to make a decision based on the test results. I will go into depth about the most common challenges and pitfalls that I have experienced throughout my career and how to avoid making the most common mistakes. After the talk, you will know what to do when someone asks you to analyse an experiment you haven't designed, how to deal with partners asking for 'directional data' and how to work successfully with engineering to ensure each test is set up correctly.