STAT/MA 416
October 3, 2011
Problem Set 18
Name:
1.
Hungry customers.
At a certain restaurant, during the working day, there are 12
customers.
Seven of them have pizza, and the other five have burgers.
Suppose that a
person is conducting a survey of three customers at the restaurant, and he conducts the
survey without replacement, i.e., he does not talk to the same customer more than once. All
possible selections of three people for the survey are equally likely.
Let
X
be the number of people in the survey who are eating pizza.
a. What is the mass of
X
?
b. Evaluate the mass at the four values where the mass is positive. (Make sure that your
four numbers sum to 1.)
c. What is the average number of people in the survey who are eating pizza?
1
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2. Harmonicas.
Dr. Ward owns quite a few harmonicas. In particular, he has 7 “Deluxe”
harmonicas and 12 “Crossover” harmonicas. Without looking at them, they have relatively
similar shapes, so he does not notice a difference between them when he reaches into his
harmonica container. Suppose that Dr. Ward grabs 8 harmonicas, without replacement, and
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 Fall '08
 Staff
 Probability, Variance, Probability theory, granola bars, Dr. Ward

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