An oil company thinks that there is a 60% chance that there is oil in the land they own. Before drilling they run a soil test. When there is oil in teh ground, the soil test comes back positive(indicating oil) 90% of the time. When there is NO oil in teh ground, the soil test is positive(indicating oil) 20% of the time.
What is the probability that a test comes back positive-indicating oil.
My ans- P(BUP)=P(B)+P(P)-P(BnP)=.900+.600-.200= 1.3
What is the probability that there is oil in teh ground, if the test comes back positive?