The Growth team wants to use controlled experiments as much as possible to determine the impact of our work on new editor retention. We will likely be measuring second-week and second-month retention.

This task is to do initial power calculations to understand our limitations with experiments in our pilot wikis, Czech and Korean Wikipedias. Given the volume of new editors that are signing up in those wikis, we want to know how long we'll need to run experiments in order to learn our impact. Given that our annual goal is to increase retention by 10%, I think we would want to be able to detect impact of 5%, but that is something we could discuss.