# 📊 Sensitivity / Specificity

Sensitivity, specificity, and likelihood ratios can be tricky concepts to understand and apply. This calculation sheet can help you better understand the meaning behind these terms.

Included in this sheet is a 2x2 table complete with calculations for the following:

### Sensitivity

Sensitivity

- The proportion of people
**WITH**the condition who get a (+) test. Also known as the**True Positive Rate**.

### Specificity

Specificity

- The proportion of people
**WITHOUT**the condition who get a (-) test. Also known as the**True Negative Rate**.

### Positive Likelihood Ratio

Positive Likelihood Ratio

- How much the odds of the condition
**increase**based on a (+) test

### Negative Likelihood Ratio

Negative Likelihood Ratio

- How much the odds of the condition
**decrease**based on a (-) test

### Positive Predictive Value

Positive Predictive Value

- If (+) test, the probability of having the condition

### Negative Predictive Value

Negative Predictive Value

- If (-) test, the probability of NOT having the condition

### Diagnostic Odds Ratio

Diagnostic Odds Ratio

- Ratio of odds of (+) test if (+) for condition relative to the odds of (+) if (-) for condition.

### Risk Ratio

Risk Ratio

- Ratio of the probability of an outcome in an exposed group to the probability of an outcome in an unexposed group.