Descriptive Statistics - Probablity - Exam, Exams of Probability and Statistics

This is the Exam of Probablity which includes Joint Distribution, Continuous Random Variables, Compute, Test Engineer Discovered, Lifetime of an Equipment, Expected Lifetime, Variance, Parameter, Independent and Identically etc. Key important points are: Descriptive Statistics, General Information, Comprehensive, Sample Spaces, Point Method, Probability, Multinomial Coefficients, Composition Method, Independence, Cumulative Distribution

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Mathematics 375 Probability Theory
Review Sheet, Final Exam
December 1, 2011
General Information
The final examination for this course will be given at 3:00 pm on Friday, December 16
in our regular class room, Swords 359. The exam will be roughly twice the length of one of
the two midterms and I will let you continue working on it as long as you want (even after
the formal end of the exam period at 5:30pm, if necessary). As was true on the midterms,
I will let you bring a sheet of information for your use on the exam for this exam, you
can place anything you want on one side of an 8.5 ×11 inch piece of paper. I will provide
copies of whatever tables from the text might be needed to work some of the problems.
Topics to be Covered
This will be a comprehensive exam all topics we have discussed this semester are
“fair game.” This includes:
1) Descriptive statistics such as the mean, standard deviation, frequency histograms, etc.
The “empirical rule”.
2) Discrete sample spaces and counting techniques (especially in connection with the
“sample point method” for the probability of an event): the m×nrule, permutations,
binomial and multinomial coefficients.
3) The event composition method” for probabilities
4) Conditional probabilities, independence of events, Bayes’ Rule, the Law of Total Prob-
ability
5) Discrete random variables: probability distribution functions, cumulative distribution
functions, expected values and variances of functions of a discrete random variable,
moment generating functions. Know the situations leading to binomial, geometric,
Poisson, and hypergeometric random variables and how to apply them.
6) Continuous random variables: probability distribution functions, cumulative distri-
bution functions, expected values and variances of functions of a continuous random
variable, moment generating functions. Know the situations leading to uniform, ex-
ponential, gamma, beta, and normal random variables and how to apply them.
7) Tchebysheff’s Theorem.
8) Multivariate probability distributions: joint densities, marginal and conditional den-
sities, expected values in this setting, conditions for independence, the covariance and
the general formula for the variance of a linear combination of random variables.
9) Using moment generating functions and the uniqueness theorem to determine the
distribution of a random variable.
10) The method of distribution functions to determine the distribution of a random vari-
able.
11) Know the statement and proof of the Central Limit Theorem.
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Mathematics 375 – Probability Theory Review Sheet, Final Exam December 1, 2011

General Information

The final examination for this course will be given at 3:00 pm on Friday, December 16 in our regular class room, Swords 359. The exam will be roughly twice the length of one of the two midterms and I will let you continue working on it as long as you want (even after the formal end of the exam period at 5:30pm, if necessary). As was true on the midterms, I will let you bring a sheet of information for your use on the exam – for this exam, you can place anything you want on one side of an 8.5 × 11 inch piece of paper. I will provide copies of whatever tables from the text might be needed to work some of the problems.

Topics to be Covered

This will be a comprehensive exam – all topics we have discussed this semester are “fair game.” This includes:

  1. Descriptive statistics such as the mean, standard deviation, frequency histograms, etc. The “empirical rule”.
  2. Discrete sample spaces and counting techniques (especially in connection with the “sample point method” for the probability of an event): the m × n rule, permutations, binomial and multinomial coefficients.
  3. The “event composition method” for probabilities
  4. Conditional probabilities, independence of events, Bayes’ Rule, the Law of Total Prob- ability
  5. Discrete random variables: probability distribution functions, cumulative distribution functions, expected values and variances of functions of a discrete random variable, moment generating functions. Know the situations leading to binomial, geometric, Poisson, and hypergeometric random variables and how to apply them.
  6. Continuous random variables: probability distribution functions, cumulative distri- bution functions, expected values and variances of functions of a continuous random variable, moment generating functions. Know the situations leading to uniform, ex- ponential, gamma, beta, and normal random variables and how to apply them.
  7. Tchebysheff’s Theorem.
  8. Multivariate probability distributions: joint densities, marginal and conditional den- sities, expected values in this setting, conditions for independence, the covariance and the general formula for the variance of a linear combination of random variables.
  9. Using moment generating functions and the uniqueness theorem to determine the distribution of a random variable.
  10. The method of distribution functions to determine the distribution of a random vari- able.
  11. Know the statement and proof of the Central Limit Theorem.

Suggestions on How to Study

Start by reading the above list of topics carefully. If there are terms there that are unfamiliar or for which you cannot give the precise definition, start by reviewing those topics. Review the class notes. Everything on the final will be closely related to something we have discussed at some point this semester. Also look back over your graded problem sets and exams. If there are problems that you did not get the first time around, try them again now, consulting the solutions on reserve in the Science Library as necessary. Then go through the suggested problems from the review sheets. If you have worked these out previously, it is not necessary to do them all again. But try a representative sample “from scratch” – don’t just look over your old solutions. Practice thinking through the logic of how the solution is derived again.

Suggested Practice/Review Problems

Look at the problems from the two previous review sheets for the topics from Chapters 1 - 5. From Chapter 5/105 (do all the computations needed to find V (Y 1 − Y 2 ) using the formula of Theorem 5.12), 147,149,151,161. Chapter 6/93,95,107,111.

Review Session

I will be happy to run a review session for the final exam. We can discuss a time in class on Friday, December 9.

Sample Exam Questions

Note: This was the final exam given in the section of this class taught in 2009. Solutions for these questions are available on the course homepage for that section – go to my personal homepage, follow links Course Homepages/Previous Course Home Pages, and look at the page for MATH 375 from Fall 2009.

I. Twenty students in a probability and statistics class were asked to report the number of pets in their families, giving the following data:

A) (10) Construct a relative frequency histogram for this data using one “bin” for each integer value. B) (10) How many of the data values are within two sample standard deviations of the sample mean? How does this compare with the “empirical rule?”

II. Suppose you have a key ring with N keys, exactly one of which is your car key. You are parked in a country lane on a moonless night and can’t see the keys or the ring. So you try the keys in your car door lock one by one until you find the right one.

independently and randomly from the two boxes, what is the probability that they will fit together?

VIII. Let X and Y be independent random variables with moment-generating functions

mX (t) = mY (t) = et

(^2) +3t

A) (10) What is the moment generating function of Z = 3X + 2Y − 4? B) (10) What is the distribution of Z?

IX. Twenty students in a probability and statistics class take a final examination inde- pendently of one another. The number of minutes each student requires to complete the exam is a random variable with an exponential distribution with mean 120 minutes. The students all start work at 8:30am. A) (10) What is the probability that at least one student out of the 20 will complete the exam by 10:00 am? B) (10) What is the distribution of the total time taken by all of the students to complete the exam?

X. Suppose Y 1 , Y 2 have joint density

f (y 1 , y 2 ) =

24 y 1 y 2 if y 1 ≥ 0, y 1 + y 2 ≤ 1 0 otherwise

A) (10) Are Y 1 , Y 2 independent? B) (10) What is V (8Y 1 − 2 Y 2 )? C) (10) Use the method of distribution functions to find the density function for U = Y 1 + Y 2.

Extra Credit (10) One form of the Law of Large Numbers states that if X 1 ,... , Xn are inde- pendent and identically distributed random variables for which E(Xi) = μ and V (Xi) = σ^2 exist, then for any ǫ > 0, lim n→∞ P (|X − μ| < ǫ) = 1.

Prove this statement without assuming anything else about the distribution of the Xi.