Relative risk

The ratio of the risk (or probability) of an event for one group to the risk of the same event for a second group.

Example

The following data were collected on a random sample of students enrolled in a Statistics course at the University of Auckland.


Attendance
    Regular Not regular Total
Course
result
Pass
Fail
83
17
19
27
102
44
  Total 100 46 146

The risk of failing for students with non-regular attendance = 27/46 = 0.5870

The risk of failing for students with regular attendance = 17/100 = 0.17

The relative risk of failing for students with non-regular attendance compared to those with regular attendance = 0.5870/0.17 = 3.5

This can be interpreted as the risk of failing for students with non-regular attendance is about 3.5 times the risk of failing for students with regular attendance.

Curriculum achievement objectives references
Probability: Levels 7, (8)