Critical Numbers

Question 1

What is the odds ratio?

Answer 1

Ratio of the probability of an event occurring to the probability of it not occurring
e.g. in a test for aspirin the odds of hypertension are the probability of hypertension divided by the probability of no hypertension

Question 2

How do we interpret the odds ratio?

Answer 2

If OR = 1 there is no difference in the groups
If the OR <1 the odds of the outcome occurring are lower in the numerator (group of interest)
If the OR >1 the odds of the outcome are greater