Variables on scatterplots look more highly correlated when the scales are increased.
Judged association between two variables represented on scatterplots increased when the scales on the horizontal and vertical axes were simultaneously increased so that the size of the point cloud within the frame of the plot decreased. Judged association was very different from the correlation coefficient, r, which is the most widely used measure of association.
Cleveland
W S
WS
Diaconis
P
P
McGill
R
R