# Thread: Calculating Posterior Probability with two variables

1. ## Calculating Posterior Probability with two variables

Hey Guys,

Calculate the posterior probability of patient having flu given cough positive and fever negative?

Sensitivity of cough for flu: 60%
Sensitivity of fever for flu: 70%
Specificity of fever for flu: 80%
Specificity of cough for flu: 50%
Prior of flu: 10%

Greatly appreciated!

Rico

2. ## Re: Calculating Posterior Probability with two variables

Originally Posted by rico
Calculate the posterior probability of patient having flu given cough positive and fever negative?
Sensitivity of cough for flu: 60%
Sensitivity of fever for flu: 70%
Specificity of fever for flu: 80%
Specificity of cough for flu: 50%
Prior of flu: 10%
Greatly appreciated!
Rico
$\displaystyle P({flu})=.10$

$\displaystyle P({cough}|{no$\_$fever})=\frac{.60+.80}{.60+.70+.8 0+.50}=.53846$

$\displaystyle P({cough}|{flu})=p({flu})*P({cough}|{no\_fever})=. 053846$

double check this!

Thanks!!