The feeling your got from looking at the graph come from the idea that the red line represent absolute values. It’s actually an average of the real value as tha

The feeling your got from looking at the graph come from the idea that the red line represent absolute values. It’s actually an average of the real value as that is a really big difference and of the reasons why it’s very easy to lie with statistics. To correct correlate the two variables (assessment and actual-score) you need to correlate the actual data, not measures of its caracteristics (average being one of them). The actual data is shown. Even by eye it’s possible to see no strong (or significant) correlation exists.