MATH 4510 Final Exam: Probability Theory, Exams of Probability and Statistics

The december 13, 2008 final exam for the introduction to probability course (math 4510). The exam covers various topics in probability theory, including marginal distributions, expected values, poisson random variables, and conditional probabilities.

Typology: Exams

2012/2013

Uploaded on 02/21/2013

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MATH 4510: Introduction to Probability
December 13, 2008
Final Exam
I have neither given nor received aid on this exam.
Name:
In order to receive full credit your answer must be complete,legible and correct. Show all of
your work, and give adequate explanations.
DO NOT WRITE IN THIS BOX!
Problem Points Score
120 pts
210 pts
315 pts
410 pts
510 pts
610 pts
715 pts
810 pts
Bonus 5 pts
Total 100 + 5 pts
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pf4
pf5
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pf9
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Download MATH 4510 Final Exam: Probability Theory and more Exams Probability and Statistics in PDF only on Docsity!

MATH 4510: Introduction to Probability

December 13, 2008

Final Exam

I have neither given nor received aid on this exam.

Name:

In order to receive full credit your answer must be complete, legible and correct. Show all of your work, and give adequate explanations.

DO NOT WRITE IN THIS BOX!

Problem Points Score

1 20 pts

2 10 pts

3 15 pts

4 10 pts

5 10 pts

6 10 pts

7 15 pts

8 10 pts

Bonus 5 pts

Total 100 + 5 pts

  1. (20 pts) A dart is thrown, and its location is given by (X, Y ), where X and Y are jointly distributed continuous random variables with joint density

f (x, y) =

2 π

e−(x (^2) +y (^2) )/ 2 ,

and the dart board is represented by the following figure, where the disks have radius 1, 2 and 3 respectively.

3

3

(a) Compute the marginal distribution function of X.

(d) If a player gets 5 points for landing a dart in the inner gray disk, 3 points for landing a dart in the black annulus, 1 point for landing a dart in the outer gray annulus, and 0 points for missing the dart board completely, find the expected number of points a player will get after throwing a dart.

  1. (10 pts) The average precipitation (in inches) in a given year in Boulder is approximately a normal random variable with mean 20 and variance 5, while the average precipitation in Vancouver is approximately a normal random variable with mean 44 and variance 6. As- suming that the yearly precipitation in Boulder is independent of the yearly precipitation in Vancouver, and given that I lived 2 of the last 3 years in Vancouver and 1 of the last three years in Boulder, What is the probability that during these three years I saw more than 100 inches of precipitation?
  1. (10 pts) A laboratory blood test is 95 percent effective in detecting a certain disease when it is present. However, the test also yields a “false positive” result for 1 percent of healthy people tested. If .5 percent of the population actually has the disease, what is the probability that a person has the disease given that they test positive?
  1. (10 pts) 5 cards are randomly chosen, without replacement, from a 52 card deck. Find the probability that at least one of each suit is chosen.
  1. (15 pts) The minute after the hour that a bus comes to a particular stop is a random variable X whose density is given by

fX (t) =

[

1 − cos

2 πt 15

)]

The minute after the hour that a particular person arrives at the bus stop is a uniform random variable Y on [0, 20]. Assume that X and Y are independent.

(a) Explain in words what the probability P {Y < X < Y + 5} signifies.

(b) What is the joint probability density function of X and Y (make sure to tell me the domain of this function).

(c) Compute P {Y < X < Y + 5}.

Bonus: If you were a salad dressing, what kind would you be? Explain.