can someone help me solve this math problem plz...
 

An oil company purchased an option of land in Alaska. Preliminary geologic studies assigned the following prior probabilities.
P(high qualith oil) = 0.60
P(medium quality oil) = 0.20
P(no oil) = 0.20

a. What is the probability 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:
P ( soil | high quality oil) = .20
P(soil | medium-quality ) = 0.80
P(soil | no oil) = 0.20
How should the firm interpret the soil test? What are the revised probabilities, and what is the new probability of finding oil?

nobodyu?

i think the anwser is invasion.

a. 80% ....

you dont have to drill for new oil sources when you can just take it. We have the 1st state in the Middle East States (Iraq) and soon we will be adding Iraq.

How do you figure that?
3 parcels of land, 60%, 20% and 20% making the overall probability of finding oil 33.33% (60+20+20/3=33.33) or you could be philosophical about it and say that since there is 60% oil in finding oil in the 1st parcel then the overall chances of finding oil are still 60%.

I know A is .80,

Now what is B

Probabily of finding no oil is 20%, so P(finding oil) = 1-P(not finding oil) so 80%

for B, use P(A|B)=P(AB)/P(B) or maybe Bayes' Theorem... don't feel like thinking...

come on think man

do your own homework.. lol

B) error - probability can`t be >1

woj its me man, do it for me :)

Actually, those probabilities could work, if for example it was:
P(soil | high quality oil) = 1
P(soil | medium-quality) = 1
P(soil | no oil) = 1

It would just mean that same soil is everywhere.. :)

woj man???

The probability of not finding oil is .20
The probability of finding high quality oil is .10
The probability of finding medium quality oil is .70

Just a guess, I hate math.

Wow are you in my management science class haha? Got the same problem I think.

The wording of the second question is fucked-up:

"The probabilities of finding the particular type of soil identified by the test follow:" -- not clear.

I'm going to assume, then, that the new set of probabilities are simply a latter-phase adjustment of the orginal set, and NOT intended to introduce any conditional probability (based on the accuracy of the test) as a function of the first.

If that's the case, then all we have is simply a RESTATEMENT of the probability set with weighted likelihood nested inside an A vs. B (binary) outcome.

The 2 possible binary outcomes are OIL=yes, and OIL=no. Since we are told that the probability of OIL=no is 20%, we must apply the remaining probabilities ONLY to the remainin OIL=yes binary contingency.

The solution is simply that the remaining 80% probability that there will be ANY oil (100% - 20% OIL=no) is itself subject to a SECONDARY probability, to be applied only in the case that ANY oil is found.

Hence, 80% probability of medium OIL + 20% probability of quality OIL = 100%, in the case ANY OIL is found.

New probability set:

MEDIUM = 64% (80% * 80%)
HIGH = 16% (20% * 20%)
NO OIL = 20%



j-

Oh, I forgot this part.

Answer: How the fuck should I know what the FIRM should do. Maybe they're just laundering money or something. And is the elem. stats student reading this book supposed to know what to make of soil sample readings taken from ONE well at 200 feet. This is a shitty textbook -- IMO.


j-

Oops, typo:

j-

e=mc squared

you have to use bayesian probabilities, I'm too lazy to turn my brain on for this though :)