Consider an oil-wildcatting problem. A decision maker has mineral rights on a pi
ID: 2725852 • Letter: C
Question
Consider an oil-wildcatting problem. A decision maker has mineral rights on a piece of land that he believes may have oil underground. There is a 30% chance that the decision maker will strike oil if he drills. If he drills and strikes oil, then the net payoff is $180,000. If he drills and does not strike oil, then there will be a $10,000 loss due to the sunk cost. The alternative is not to drill at all, in which case the decision maker's net payoff is $0.
Before the decision maker drill he might consult a geologist who can assess the promise of the piece of land. The geologist can tell the decision maker whether the decision maker's prospects are "good" or "poor". But she (the geologist) is not a perfect predictor. If there is oil, the conditional probability is 0.9 that she will say good. If there is no oil, the conditional probability is 0.85 that she will say poor.
What is the maximum amount that the decision maker (assume he is rational) is willing to pay the geologist for her information? (Calculate EVSI.)
Explanation / Answer
There are 30% chances you will get oil its mean other 70% chances you will not get oil. P(oil) = 0.30 and P (No oil) = 0.70
30% chance of oil : compare both alternatives
Drill will give $180,000
Don’t drill will give $0
Which one is better ?
Drill is better (0.3 x 180,000)
80% chance of NO oil : compare both alternatives
Drill will give $-10000
Don’t drill will give $0
Which one is better ? Don’t Drill is better (0.7 x 0)
EV(with help of perfect Information) will be
0.3 x 180,000 + 0.7 x 0 = 54,000
P(“good” | oil) = 0.90 P(oil) = 0.3
P(“poor” | no oil) = 0.85 P(no oil) = 0.7
Chance nodes: EV(6) = 0.72 x 180,000 + 0.28 x -10000 = 126,800
Chance Node EV(2) = 0.28 x 126,800 + 0.72 x 0 = 35,504
EV(8) = 0.3 x 180000 + 0.7 x -10000 = 47,000
The expected value of drilling is $36,000, versus $0 for not drilling, so choose to drill
EVSI = EV(with help of Consult Geologist) - EV(Help) = $35,504 - $47,000 = $11,496
G= Good State of Nature Prior Probabilities Conditional probabilities Joint Probabilities Posterior Probabilities Sj P(Sj0 P(G/Sj) P(G and Sj) P(Sj/G) Oil 0.30 0.90 0.27 0.72 No Oil 0.70 0.15 0.105 0.28 P(G) 0.375 1