QC Selection Grid, Square 2
This is not a good situation because you have frequent problems, however, medically important errors are moderate in size and may be detectable by using a five rule procedure with N=4. The 8x rule should be used across runs and interpreted as a rejection rule. The power curves below show the rejection characteristics within a run (R=1) and across two runs (R=2):
Plot your critical-error on the x-axis of this power function graph. Draw a vertical line from that point to intersect the power curves. Where the curves and critical-error meet indicates how much error detection each control rule will provide.