Easy $5 for solving math problem.
 

First person to solve this correctly will get $5. I cant get the answer myself for this one..


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?(I know the answer, 0.80)

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?

the answer is "There's a 100% probability of finding ICE"

lol

8char

Oil will be $5 a gallon soon!

Pick C :thumbsup :1orglaugh

We'll just bomb them and take the oil.

Want my email addy to send the $5?

!!!!!!!!! come on guys, $10 now :)

Damn, I'm paying almost $5 for 1 quart of Quaker State so that's a pretty damn good deal!

do your own homework!!!!!!!!!!!!

I'm waiting until its $20 :)

I can tell u 1 thing atleast, there is still 0,8 chance on finding oil....

Ok, I'm in a good mood.
First off your first answer is wrong.

It's not 0.80, you don't just add the first 2 probabilities and ignore the second set of data given. You need to multiply the 2 probabilities and then sum them up:

So, (0.60 * 0.20) + (0.20 * 0.80) + (0.20 * 0.20) = .12 + .16 + 0.4 = 0.68

So you actually have a 68% chance of discovering oil now.
PS: It's been 2 years since I did stats, so don't hold me to this answer. If you fail, its your own fault for not paying attention in class.

WG

a. P(finding oil) = 1 - p(no oil) = 1 - 0.20 = 0.80

b. Test interpretation: We can see the conditional probability for the medium quality oil goes up while the other two go down. That means doing such positive test can improve your chance to find the medium quality oil.

New probability of finding oil is 0.8125 (see below)

0.5 * 0.2 + 0.2 * 0.8 / 0.5 * 0.2 + 0.2 * 0.8 + 0.3 * 0.2 = 0.8125


Send the money to the charity of Mr.Izzz's choice, since after all he is right in saying that you should "do your own homework!!!!!!!!!!!!"

Is my answer right? Of course. I googled it. I have the source for this answer if needed.

:winkwink:

Eigther it's a missprint and it should have been .20 .60 .20 in wich case the probability is still .80
or..
probability 1.0 = they found oil

The revised probabilities are now:
Note: P(finding oil) = my answer from part (a) = 0.68

P(high qualith oil) * P ( soil | high quality oil) / P(finding oil) = 0.1765
P(medium quality oil) * P(soil | medium-quality) / P(finding oil) = 0.2353
P(no oil) * P(soil | no oil) / P(finding oil) = 0.0588

WG

seven - the answer in seven

OLD RESULTS (GIVEN):
P(soil | high quality oil) = .20
P(soil | medium-quality ) = 0.80
P(soil | no oil) = 0.20

NEW RESULTS (CALCULATED):
P(high qualith oil) * P ( soil | high quality oil) / P(finding oil) = 0.1765
P(medium quality oil) * P(soil | medium-quality) / P(finding oil) = 0.2353
P(no oil) * P(soil | no oil) / P(finding oil) = 0.0588


The firm should intepret the results as:
The conditional probability of finding high quality, medium quality and no oil have all dropped (although by different ratios).

WG

Remember the second values werent given until question B..

QUestion A assumes u use the first set of values..

HUHHHHH?? :eek7 :Oh crap

Can i get the source?

If I can't count on my fingers and toes ..forget it :(

P ( soil | high quality oil) = .20
P(soil | medium-quality ) = 0.80
P(soil | no oil) = 0.20

how can that be? it adds up to 1.20, not 1...

page 24...

http://www.1493.com.tw/upfiles/skill01100857753.pdf

My answer simply changes the variables in part (1) ... part (2) is the same as yours.

:)

Umm dude there is also another source with a totally different answer:
grr wtf..

4 of my friends got different answers for this. seems like the question is not 100% clear.

Welcome to Stats :)
No two people will get the same two answers, lol.
WG

LOL ya there's 2 sources (Professors) with same question online, both of them have different answers,

WTF really

Here's one where the question is almost worded identically (different numbers):

http://stat.wharton.upenn.edu/~pzhang/stat101/HW02.doc (Question on bottom)

http://stat.wharton.upenn.edu/~pzhan...01/HW02sol.doc (Answer on bottom).

Answers seem to be similiar to mine.
WG

Ya but see

[What is the probability of a positive soil test?
P(+)=P(+ | high quality oil)* P(high quality oil)+P(+ | medium quality oil)* P(medium quality oil)+P(+ | no oil)* P(no oil)=0.32]

Im not looking for the PROBABILITY of a positive SOIL TEST...
Thats what you/they calculated.


Question says probability of finding oil.. So how can you include the probability of finding no oil into the calculation

xxweekxx, you are a clown :1orglaugh

Ya i am.lol i was gonna have u do it but i figured no way to verify your answer.. see what i mean??

so far 5 people got 5 diff answers

Wow, i was a science person in high school, and still is. I hate math! Calculus wasn't as bad as many made it sound.

The oil rig was shut down because Onook got into a fight with his wife, went postal, and killed 12 of the 16 employees!

The answer is the two trains will take 2 hours before they crash into each other....wait...wrong college problem :)

at least a .80% chance of finding some kind of oil, heh well i gave it a shot

wow! a lot of math wizards!!!

I thought GFY was smart

is there still that $5 up for grabs??

What gave you that impression? LOL
WG

Think again.

After numerous calculations, I have concluded the answer is: Penis