Dear SAS community,   I am running PLS on spectra data and I am trying to clarify how root mean press is calculated in full leave-one-out cross validation. I have the following model: PROC PLS DATA=df cv=one; MODEL depvar=nm400-nm1900; OUTPUT out=outputdata PRESS=press; run;   As I understand it, the OUTPUT PRESS option gives the residual value between the observed and predicted for each observation when that observation is "held out" from the data set. First, is this correct? Now if I calculate the root mean press for the data set from the output dataset PRESS values, the value is different than the root mean press for the number of factors which minimizes PRESS. From the analyses I've seen, the root mean PRESS output by SAS seem to vary between 0 and 1 (or at least near 1), so my guess is there is some sort of normalization occuring in these calculations. I can't find any source detail if or how SAS is normalizing the root mean PRESS values. I've also tried a multitude of transformations to try and replicate the root mean PRESS output by the model to no avail. Can anyone shed any light on this?   Thank you, Jordan   ... View more