Table.

False alarm rates using 90% two tailed confidence interval: probabilities of concluding that failure rate in worst of possibly many series exceeds threshold value of 25% when it equals 25% or 20%. Results of computer simulations of series with 100 operations per series

Probability of false alarm	Failure rate
	National average (25%)	Better than average (20%)
Single series tested once	0.05	0.002
Single series tested after every failure	0.2	0.05
Four series per operator tested after every failure	0.59	0.20
Two operators per hospital (8 series)	0.74	0.29
Four hospitals (32 series)	0.995	0.75