An overlooked property of plot methods

An interesting and often overlooked property of the MLR least-squares method is discussed. Here it is shown how the observed vs. calculated and calculated vs. observed plots, which are usually presented as equivalent, in fact they are not. Due to the inherent properties of the MLR procedure, it is shown that the slope of the calculated vs. observed plot is r 2, as the slope of the experimental vs. calculated plot is just 1. This behaviour also has direct consequences to the corresponding residual plots.