Calculating NNH

Suppose both Headeeze and Noache can also cause harm and increase the number of major bleeds in patients. The control and experimental event rates for the incidence of bleeds with Noache and Headeeze are shown in this table.

The absolute risk increase (ARI) and number needed to harm (NNH) for Headeeze have already been calculated. The number needed to harm (NNH) for Headeeze is 13 (i.e. 13 people need to be treated with Headeeze for 1 person to experience a bleed or harm).

Calculate the absolute risk increase and the numbers needed to harm for Noache, and enter the values into the table below. Select 'Submit' to check your answer.
Harms Placebo Headeeze ARI NNH
Event rate 1% 9% 8% (9-1%) 13 (1/8% or 100/8)
Benefits Placebo Noache ARI (%) NNH
Event rate 2% 5%