C. 5 – Explanation
Remember to calculate the odds, rather than risk, initially:
Odds of a golfer developing medial epicondylitis = 30 / 30 = 1
Odds a non-golfer developing medial epicondylitis = 10 / 50 = 0.2
The odds ratio is therefore = 1 / 0.2 = 5
Odds and odds ratio
Odds are a ratio of the number of people who incur a particular outcome to the number of people
who do not incur the outcome. The odds ratio may be defined as the ratio of the odds of a particular
outcome with experimental treatment and that of control.
Odds ratios are the usual reported measure in case-control studies. It approximates to relative risk if
the outcome of interest is rare.
For example, if we look at a trial comparing the use of paracetamol for dysmenorrhoea compared to
placebo we may get the following results
| Total number of patients | Achieved = 50% pain relief | |
| Paracetamol | 60 | 40 |
| Placebo | 90 | 30 |
