[R] qqplot

Peter Flom peterflomconsulting at mindspring.com
Mon Nov 2 18:33:37 CET 2009


John Fox <jfox at 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



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