WILL MEDAL!
Jason inherited a piece of land from his great-uncle. Owners in the area claim that there is a 45% chance that the land has oil. Jason decides to test the land for oil. He buys a kit that claims to have an 80% accuracy rate of indicating oil in the soil. If the test predicts that there is no oil, what is the probability after the test that the land has oil?

Question

lyssakat · Answer

0.1698

0.2217

0.5532

0.7660

lyssakat · Answer

Its not C. i know that

misty1212 · Answer

hi
let me check my answer with a calculator, see if it gives one of your answers

misty1212 · Answer

yes it does, so first off, it is clear that this probability should be low?  tests negative, but even so has oil?

lyssakat · Answer

Okay Do i need to use any type of formula?

misty1212 · Answer

yes, it is called Baye's formula
have you seen it?

misty1212 · Answer

it is a form of conditional probability

lyssakat · Answer

Ive probably seen it before but right now im drawing a blank.

misty1212 · Answer

ok we can reason it out anyway
do you know this formula for conditional probability $$P(A|B)=\frac{P(A\cap B)}{P(B)}$$?

lyssakat · Answer

no i dont :(

misty1212 · Answer

dang, then you are pretty much out of luck!

lyssakat · Answer

Oh dang okay

misty1212 · Answer

it says that the probability of A given B is the probability of A and B divided by the probability of B

misty1212 · Answer

so we have to compute each of those in the case where A is "has oil" and B is "test is negative"

misty1212 · Answer

it is not that hard
ready?

lyssakat · Answer

im sorry i wasnt here to respond back! Thank you for trying to help!