Odds And Odds Ratio

Question 1

Odds definition Important

Answer 1

Type of probability: It’s is used for looks at binary outcomes i.e. disease occurs, or it does not.

Odd = Probability Event Occurs (p) / Probability Event Does Not Occur (1-p)

Question 2

Odds ratio definition Important

Answer 2

Compare the odds of an outcome occuring between two groups - usually the group with the exposure/treatment and a control group

Odds Ratio = Odds of an Event (Condition A) / Odds of an Event (Condition B)

Question 3

How to interpret odds ratio

Answer 3

Odds Ratio = 1: The odds of the event occurring in one condition equal the odds of it happening in the other condition. No association.
Odds Ratio > 1: The events odds are higher for the group/condition in the numerator. This is often a risk factor
Odds Radio < 1: The probability of the outcome occurring is lower for the group/condition in the numerator. This can be protective factor or treatment provided

Question 4

Absolute risk

Answer 4

The probability of an events occuring in a group
Formula: Number of events/Total population

Question 5

Relative risk

Answer 5

The ratio of the probability of an event occuring in an exposed group compared to an unexposed group
Formular: Risk in exposed group/ Risk in unexposed group