A hierarchy of evidence (or levels of evidence) is a heuristic used to rank the relative strength of results obtained from scientific research. I've created a version of this chart/pyramid applied to CRO which you can see below. It contains the options we have as optimizers and tools and methods we often use to gather data.
This is a bonus episode with Emily Robinson (Senior Data Scientist at Warby Parker) en Lukas Vermeer (Director of Experimentation at Booking.com). In her earlier session that day, Emily said that real progress starts when you put your work online for others to see and comment on which in this case was about Github. Someone from the audience wondered how that works out in larger companies where a manager or even a legal department might not be overly joyous about that to say the least so I asked Emily about her thoughts on that. Recorded live with audience pre-covid-19 at the Conversion Hotel conference in november 2019 on the island of Texel in The Netherlands. (oorspronkelijk gepubliceerd op https://www.cro.cafe/)