The post ends with a link to the actual paper. The paper's graphs do have labeled axes. While I agree the blog post should have labeled them too (and we'll fix

The post ends with a link to the actual paper. The paper's graphs do have labeled axes. While I agree the blog post should have labeled them too (and we'll fix that), if you really want to understand what's going on, you should read the paper anyway — you're not going to get out of a few paras of appetizer what took several pages of research paper to explain. For your convenience, here's the paper link again: https://cs.brown.edu/~sk/Publications/Papers/Published/wkf-who-tests-testers/ https://cs.brown.edu/~sk/Publications/Papers/Published/wkf-w... I don't think the visualization is all that "unusual": it's a standard presentation called a KDE [https://en.wikipedia.org/wiki/Kernel_density_estimation https://en.wikipedia.org/wiki/Kernel_density_estimation]. If you just want to understand the graphs, the x-axis is Rate and y-axis is Density, because it's a KDE (as the text says just above the first graph). Think histogram (which it also says): How many students had this particular true-positive/true-negative rate? But I think you really will understand this better by reading the paper.