John Fox <j...@mcmaster.ca> wrote > >I assumed that Carol wanted to compare the shapes of the distributions and >to adjust for differences in centre and spread. To put a line through the >quartiles or to base a line on the medians and IQRs is more robust than >using the means and sds. > Hi John
Indeed it is. It all depends on what she wants to use the QQplot for, and what she wants to adjust for. But I would guess (and I haven't done any simuls) that the method with mean and sd will usually be pretty close to the one with medians and IQRs. Maybe I will look at it a bit. Peter Peter L. Flom, PhD Statistical Consultant Website: www DOT peterflomconsulting DOT com Writing; http://www.associatedcontent.com/user/582880/peter_flom.html Twitter: @peterflom ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
