The open question this raises to me is why a DK=true set of data would show up with the same graph as a uniformly random set
What I'm really missing is a plot of the data without the aggregation. I find it very strange that X is broken down into quartiles but Y isn't, and when in quartiles, people estimated their skills relative to each other quite well: the line still goes up, and from bottom to top, would be a perfect X to X corelation
Uniformly random data means that someone’s perception of their ability is uncorrelated with their actual ability, which is exactly what DK=true is saying!
What I'm really missing is a plot of the data without the aggregation. I find it very strange that X is broken down into quartiles but Y isn't, and when in quartiles, people estimated their skills relative to each other quite well: the line still goes up, and from bottom to top, would be a perfect X to X corelation