Table 1

Data from a cancer prevention trial for investigating assumptions of constant risk difference and relative risk when risk groups change.

Placebo group

Tamoxifen group

Variable

risk group

cancer

at risk

cancer

at risk

age at entry

1

≤ 49

68

10149

38

10045

2

50–59

50

7912

25

8040

3

>60

57

7719

26

7782

predicted risk

1

≤ 2.00%

35

6318

13

6311

2

2.01–3.01%

42

8108

29

8262

3

3.01–5.00%

43

7313

27

6959

4

≤ 5.01%

55

4142

20

4425

family risk

1

0

38

5891

17

5724

2

1

90

15000

46

15182

3

2

37

4263

20

4211

4

3

10

729

6

855

Cancer is invasive breast cancer. Predicted risk is the 5-year predicted risk. Family risk is number of first degree relatives with breast cancer. Data are from Table 5 of [5] with number at risk computed by dividing number of breast cancers by reported breast cancer rate.

Baker et al. BMC Medical Research Methodology 2004 4:24   doi:10.1186/1471-2288-4-24