Odds

What is odds

In general, odds are the ratio of the number of successes to the number of failures.

For example heart attack data with odd=1.74, we interpret it as:
For every heart attack there are 74 instances of not having a heart attack.

What is odd ratio

In general, odd ratio is a measurement of odds of two groups, it has formula$$\frac{\text{odd ratio of first group}}{\text{odd ratio of second group}}$$

Remark: Note that when odd ratio =1 it implies that there are not association between two groups