Originally Posted by

**dori1123** I am not sure if that's correct.. I am understanding the problem this way:

If the polygraph is 92% reliable when given to someone who is guilty, and 95% reliable when given to someone who is innocent, this means that the probability of a suspect tested guilty given that he/she is actually guilty is 0.92 and the probability of a suspect tested innocent given that he/she is actually innocent is 0.95.

Let TG = tested guilty, TI = tested innocent

$\displaystyle P(TG|G)=0.92, P(TI|G)=0.08, P(TI|I)=0.95, P(TG|I)=0.05$

So $\displaystyle P(TG)=P(G)P(TG|G)+P(I)P(TG|I)=(0.1)(0.92)+(0.9)(0. 05)=0.137$

Right?