The formula to calculate the post-test probability is:
\[ \text{Pre Test Odds} = \frac{P}{1 - P} \]
\[ \text{Post Test Odds} = \text{Pre Test Odds} \times LR \]
\[ \text{Post Test Probability} = \frac{\text{Post Test Odds}}{1 + \text{Post Test Odds}} \]
Where:
Let's say the pre-test probability (P) is 0.012 and the likelihood ratio (LR) is 5. Using the formula:
\[ \text{Pre Test Odds} = \frac{0.012}{1 - 0.012} = 0.012 \]
[ \text{Post Test Odds} = 0.012 \times 5 = 0.06 ]
\[ \text{Post Test Probability} = \frac{0.06}{1 + 0.06} = 0.0566 \]
We get a post-test probability of approximately 0.0566 or 5.66%.
