Honestly, this is not my area of expertise (I'm a software person), so I'm going to avoid speculating too much. Standardized testing is indeed one way that we

Honestly, this is not my area of expertise (I'm a software person), so I'm going to avoid speculating too much. Standardized testing is indeed one way that we can demonstrate efficacy: https://www.khanacademy.org/about/impact https://www.khanacademy.org/about/impact That page also includes studies that talk about course pass rates. I don't know if our efficacy work necessarily changes "mastery" definitions, but I can imagine (but have no direct involvement with) these studies and smaller-scale studies are used by our pedagogy and course creators to improve how we approach the material. Again, though, not my area of expertise :)