Table 1

Different ways to describe 'risk'

Placebo arm (n = 1000)
Treatment arm (n = 1000)
Relative risk reduction
Absolute risk reduction
Number needed to treat

200
100
50
10
10
20
10
50
1
100
2
1
50
0.1
1000

In this example, a treatment trial involving 2000 patients, 'relative risk reduction' remains the same while 'absolute risk reduction' and 'number needed to treat' show differences in the appreciation of risk as the success of the treatment is modelled to change.

Boyd and Jackson Critical Care 2005 9:390   doi:10.1186/cc3057