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STAT/MA 416
November 11, 2011
Problem Set 32
Name:
1.
Each of the 30 students in a class each orders a package. They assume that the waiting
time (measured in weeks) for the packages are independent exponential random variables,
with average waiting time of 1
/
2 for each package.
What is the approximate probability that the total waiting time exceeds 14 days?
1
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When the students in question #1 eventually receive their packages, sometimes they
are happy with the items they ordered, and sometimes they are not. Suppose that a stu
dent is happy with her/his own package with probability 0
.
60, independent of the happi
ness/unhappiness of the other students.
What is an estimate for the probability that 20 or more of the students are happy with
their packages?
2
3.
In planning for an event, the planner estimates that nobody will be on time, but nobody
will be more than 10 minutes late. So he estimates that the time (in minutes) a given person
will be late has density
f
X
(
x
) =
(10

x
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This note was uploaded on 02/28/2012 for the course STAT 416 taught by Professor Staff during the Fall '08 term at Purdue University.
 Fall '08
 Staff
 Probability

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