(a) What is the probaility of finding oil ?
(b) After 200 feet of drilling on the first well, a soil test is taken. The probabilities of finding the particular type of soil identified by the test follow.

I haven't attempt the problem. I was out sick for this day of class and my tutoring session is not schedule until next week, but I need to understand and do this problem in order to move ahead to the next problems. I read the problem and thought that, they did not give me enough information to complete it.

Yes, part (b) we are suppose to use Bayes theorem!

For clarification:

For Part A, How would I show I show it as a fraction!
Would it be 1-.30 = .7[/B]

What Bayes' formula does is it modifies or revises the probability of the occurrence of an event, based on "additional" information. Originally, the probability of high-quality oil was tought to be 0.5. Then they took a soil sample 200 feet down, and this is the "additional" information. You are asked to determine how this additional information revises the probability of an event.

In the denominator of the Bayes formula, you have P(A|B)*P(B) + P(A|B')*P(B'), the second part is different from the first part. B' is the complement of B, P(B')=1-P(B).

I still did not get it because the first problem identify no oil as 030, but then addt information was given and teh probabilities change. So I thought I would be working from the second set of new probabilities.