Table 3

Hypothetical data for two ordered markers, A and B

Subjects without cancer (N = 1000)

Subjects with cancer (N = 100)

A = 1

A = 2

A = 3

B only

A = 1

A = 2

A = 3

B only

B = 1

640

80

80

800

20

0

0

20

B = 2

80

10^a

10^a

100^e

0

20^b

0^b

20^f

B = 3

80

10^a

10^a

100^e

0

0^b

60^b

60^f

A only

800

100^c

100^c

20

20^d

60^d

For A and B combined; ^aFalse positive rate (FPR) of indicated region (10+10+10+10)/1000=. 04; ^bTrue positive rate (TPR) of indicated region = (20 +0+0+60)/100=. 80 For A only; ^cFalse positive rate (FPR) of indicated region =(100+100)/1000=. 20; ^dTrue positive rate (TPR) of indicated region = (20+60)/100=. 80 For B only; ^eFalse positive rate (FPR) of indicated region =(100+100)/1000= .20; ^fTrue positive rate (TPR) of indicated region = (20+60)/100=.80

Baker et al. BMC Medical Research Methodology 2002 2:4   doi:10.1186/1471-2288-2-4