Course Content


9 - How Far can Your Mean Shift



Benchmarking measurement procedures using TEA and the current method’s performance allows a laboratory to identify which methods are meeting quality specifications and which are not. In this activity, Sigma-metric and Critical Systematic Error (ΔSEc) are introduced.  Participants will review a site’s monthly summary report and perform an investigational analysis using instrument records and QC charts.

Key Message

  • SEc indicates how far the mean can shift before quality performance requirements are exceeded.
  • Benchmarking methods using a Sigma scale allows a laboratory to use their resources wisely.
  • Good recordkeeping is essential in resolving QC problems.

Self Assessment

Can you: 

  • Describe how SEc and Sigma indicate method performance relative to quality performance goals?
  • Calculate SEc and Sigma?
  • Use information gleaned from records to troubleshoot a QC issue?