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MATH 121 DISCUSSION WEEK 13 WORKSHEET
1)
There are 3 white socks and 5 black socks in a drawer and you pick two socks at random
without replacement. Suppose you deﬁne a random variable as the number of white socks you
draw.
(a) Determine the probabillity distribution of this random variable and organize it in a table.
(b) Plot the probability distribution for this random variable.
(c) What is the expected value for the number of white socks you would draw if you drew 2
without replacement each time?
2)
A roulette wheel has 18 red compartments, 18 black compartments, and 2 green compartments.
Suppose you bet $5 that a ball will land in one of the green compartments. If it lands in a green
compartment, then you win $50.
(a) Write a table for the random variable of change in net earnings.
(b) Plot the probability distribution for this random variable.
(c) What is the expected monetary value you can gain or lose from making this bet? Is it in
your best interest to keep making repeated bets?
(d) If the answer in part (c) is ”no,” then what is the amount of money that should be paid
out to you in order to make repeated bets that the ball will land on a green compartment
worthwhile?
3)
Now suppose that you are playing a modiﬁed version of the roulette game above, and this
time, you put up $8 to play any round. If it lands on green (0 or 00), you win $50; if it lands
on a number 1 through 10 (out of 36 nonzero numbers), you win $10, and if it lands on an even
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This note was uploaded on 12/07/2010 for the course MATH Math 121 taught by Professor Beaulieu during the Fall '10 term at UMass (Amherst).
 Fall '10
 Beaulieu
 Math, Probability

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