SYST/STAT 664: Homework Assignment 2
due February 5, 2007
Homework is due at class time on the date indicated. You may submit on paper or electronically
via Blackboard. Please make sure your name is on every page of the assignment, and it is clearly
marked which question you are answering. Your response will be graded for correctness and
clarity.
1. Problem 3 of Assignment 1 is concerned with the decision of whether to administer sanctions
to an individual who may have considered a security violation. We have the following losses:
• Do not administer sanction; individual is innocent loss = 0
• Administer sanction; individual is guilty loss = 1
• Administer sanction; individual is innocent loss = 10
• Do not administer sanction; individual is guilty loss = 100
We can obtain evidence that has 80% sensitivity and 85% specificity.
a. Find the range of prior probabilities for which considering the evidence results in
lower expected loss than ignoring or not collecting the evidence.
b. There is a loss associated with collecting the evidence (dollars, time spent, emotional
distress). As a function of the prior probability p, find the maximum loss for which
running the test could be justified.
2. In an experiment, subjects were given the choice between two gambles:
Gamble 1:
A: $2500 with probability 0.33 B: $2400 with certainty
$2400 with probability 0.66
$0 with probability 0.01
Suppose that a person is an expected utility maximizer. Set the utility scale so that u($0) = 0
and u($2500) = 1. Denote u($2400) by x. For what values of x would a person choose
Option A? For what values would a person choose Option B?
Gamble 2:
C: $2500 with probability 0.33 D: $2400 with probability 0.34
$0 with probability 0.67 $0 with probability 0.66
For what values of x would a person choose Option C? For what values would a person
choose Option D? Explain why no expected utility maximizer would prefer B in Gamble 1
and C in Gamble 2.
This problem is a version of the famous Allais paradox, named after the prominent critic of
subjective expected utility theory who first presented it. Many people’s choices violate