# Odds Ratio

Start is the Contingency Table of 2 * 2. "Use" means "Use of medicine".

## Table of Ratio

In risk analysis a table of ratio (probability) is made from contingency (frequency) table.

After that, we compare the ratio.

By the way, in the discussion of ratio, we often forget the effect of volume of sample.

## Difference of Ratio

Difference of ratio is popular index.

Hypothesis Testing for Difference of Ratio is used to consider the effect of volume of sample.

## Risk Ratio (Ratio of Ratio)

Ratio of ratio is called "Risk ratio" or "Relative risk".

## Odds

Odds is the ratio of probability of occur and not occur.

Logarithm of Odds is called " Logit ".

## Odds Ratio

Odds ratio is the ratio of 2 odds.

### Easy Calculation

Odds and Odds ratio are also calculated without p and q.

### Logarithm of Odds Ratio

Logarithm of odds ratio has the meaning "Difference of Logit" And this meaning is useful to consider the use case of logarithm of odds ratio.

## Compare Indexes

I made Heat Map to compare indexes.