For a QC sample this is an estimate of the theoretical limiting value towards which the average of results collected from a single in-statisticalcontrol measurement system under site precision conditions tends as the number of results approaches infinity.
- Note: The SEV is associated with a single measurement system; for control charts that are plotted in actual measured units, the SEV is required, since it is used as a reference value from which upper and lower control limits for the control chart specific to a batch of QC material are Constructed.