Using Six Sigma

The sigma value for a test is a good indication of its process capability because it considers both bias and imprecision. Unfortunately, most clinical laboratory tests are below six sigma processes.

So how is six sigma achieved? The obvious answer is to choose a test method with a six sigma process. Laboratories can take steps to control precision through proper training, instrument maintenance, and so on; however, to a large extent, method precision is a function of instrument methodology.

While method precision may not be controllable, a QC procedure can be chosen that detects small changes in the testing system so that reject runs having defects are identified and corrective action taken.

Note: The optional Westgard Advisor™ online calculates sigma values and displays them on the Grid and Chart options on the Design QC Rules dialog box. The sigma value also appears on the Westgard Advisor™ online Report.