nsider the tests sequentially. This is possible because the ultrasound test and the mammography are conditionally independent, i.e. P(U+ IB) = P(U+ IB & M+). Now we have: — • (I,000) women breast cancer ( 100 I N M-1 20 ) fiTh c m \-1 % 1Th 76 ( 4 19 ) 1 no breast cancer 950 M+ 8950 M- (