|
|
|
|
|
Laboratories often apply the 1-2s rule, which yields a false rejection rate of 5% for N=1, 9% for N=2, and 14% for N=3 (where N is the number of control materials tested in the run).
When using the 1-2s rule, some laboratories think it is reasonable to simply repeat the test for the control. However, with carefully chosen SPC rules, this approach is unnecessary. As an example, consider that the false rejection rate for a 1-3s rule is only 0.3%. It is also important to remember that even if the repeat value is within control limits and the run is accepted, it is possible that a problem is being ignored until a future run.
See Also |