# QC Selection Grid, Square 7

## MULTIRULE CHOICE:

You have few problems, but medically important errors are small and difficult to detect, therefore you need to increase the number of rules to four and apply the 41s rule across two runs (R=2) as a rejection rule. The power curves below show the rejection characteristics within one 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.