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PSTAT 5E
Name:
Summer 2009
Perm
˖
Midterm 2
Please follow the instructions carefully:
x
You have 75 minutes to complete the exam, and you should attempt all questions.
Be
sure to fully explain your answers.
Answers without work will receive no credit.
x
Anyone found copying off of another student’s exam or consulting their textbook or
notes during the exam will be given an “F” for the course.
x
You may use a calculator on the exam, but you may not use cell phone/pda/mp3 player as
a calculator.
x
If you have two answers to a single question, you must crossout the answer you don’t
want graded and circle the answer you want graded.
If you fail to do this, you will
receive a zero on the problem.
Please read each question carefully and good luck!
1.
[5 points] The length of time it takes students to complete a statistics
examination is uniformly distributed and varies between 40 and 60 minutes.
(a). Find the mathematical expression for the probability density function.
[1’]
(b)
Compute the probability that a student will take between 45 and 50 minutes to
complete the examination.
[2’]
(b).What is the expected value and variance of the amount of time it takes a student
to complete the examination?
[2’]
2.
[5 points] John parks cars at a hotel. On the average, 6 cars will arrive in an
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 Fall '08
 EduardoMontoya

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