RE: Applicability of SPC to Intra and Inter Assay controls

["Mark Bailey" <Mark.Bailey@sas.com>]

These suggestions are great!

Be careful about what data you combine together in a rational subgroup. Usually control samples or standards are run in duplicate or more so these are natural subgroups. This way you can study the intra- and inter-group variation.

You could also chart the subgroup means of all the controls and standards for a given assay together in a multivariate chart to see if changes occur in concert.

Note there is a lot of information about control chart practice in this specific area by NCCLS (http://www.nccls.org/) and by Jim Westgard (http://www.westgard.com/).

I apologize in advance if these ideas have already been suggested by others. I have not been able to carefully monitor this thread recently.

-Mark

Mark Bailey
Statistical Training & Technical Services
SAS Institute