Distribution Quiz Solutions
1. Jim failed his math exam. So to prepare for the final exam, he decides he wants to find a tutor who
passed the math exam in the past. The probability of a student passing the math exam was 1/3. He asks
every student he encounters if they have passed the math exam until he finds the first student who has
passed the exam. Let
X
denote the number of students he asks until he encounters the first student who
passed the exam.
The random variable
X
has a
geometric
distribution and its parameter is
p
= 1/3.
2. Erica wants to make 5 batches of rice crispy treats for her
Lifetime
girls night but realizes that she
has no marshmallows. Knowing her ten neighbors well, she determines that the probability of a
neighbor having a bag of marshmallows is 2/5 and the events that each neighbor has marshmallows
are independent. Let
X
denote the number of bags of marshmallows that Erica can mooch off of her
ten neighbors.
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 Spring '09
 LisaMarano
 Probability, Probability theory, Binomial distribution, Discrete probability distribution, Erica

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