# How to Calculate Odds Ratio?

How do you find the odds ratio?

## Odds Ratio Calculation

Odds Ratio is an important static used in clinical research and decision-making. It aids clinicians to decide which treatment has the best odds for benefiting the patient. As this is a simple strategic, it is calculated manually to determine odds of a particular event for a patient. It also helps to evaluate whether the chance of certain event or outcome is the same for two groups. The calculation is made in 2x2 Contingency Table. Here is the simple step by step tutorial that teaches how to calculate Odds Ratio (OR).

**Formula:**

**Odds ratio = ( a / c ) / ( b / d )**

**Where, **

a,b = Positive Test Values

c,d = Negative Test Values

**Step 1:**Consider that a study made among the women in middle ages who is taking health supplements for breast cancer. As a result, 40 were found positive with the result and remaining 60 were tested negative with the effect of the supplement. Similarly, statistics also collected from women who does not taken health supplements, where 45 tested positive and 55 are negative. Now what would be the odds ratio?

a = 40

b = 60

c = 45

d = 55

**Step 2:** Substituting the given values in the formula.

Odds ratio = ( a / c ) / ( b / d )

= (40 / 45) / (60 / 55)

= 0.888 / 1.090

**Odds Ratio = 0.8146**

Use our online **odds ratio calculator** for your personal reference.

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