MATH 340, Study Guide for the Final Exam

12/05/2015

Test coverage

1. Combinatorial Analysis
   1. The Basic Principle of Counting (1.2)
   2. Permutations, Combinations, Multinomial Coefficients (1.3-5)
   3. The number of Integer Solutions of Equations (1.6: Propositions 6.1, 6.2)
2. Axioms of Probability
   1. Sample Space; Outcomes; Events. Operations on Events (2.2)
   2. Axioms of Probability (2.3)
   3. Properties of Probability (2.4)
   4. "Classical Definition of Probability": Sample Spaces with Equally Likely Outcomes (2.5: Examples 5a-j,m,n; skip the rest)
   5. Probability as a Measure of Belief (2.7: read this section)
   6. Skip Section 2.6
3. Conditional Probability and Independence
   1. Conditional probability: definition and basic properties (3.1-2)
   2. Formula of compound probabilities. Bayes' formula (3.3: Examples 3acdi; Prop. 3.1, Examples 3klmn; rest can be skipped)
   3. Independent events (3.4: Examples 4abce; Prop. 4.1)
   4. Further Properties of Conditional Probability (3.5; Formula 5.1)
   5. Independent Trials (3.4: Definition of independent trials; Examples 4f,h,j; rest can be skipped)
4. Random Variables
   1. Random variables: examples (4.1)
   2. Discrete random variables: probability mass function, cumulative distribution function (4.2)
   3. Expectation of a random variable (4.3)
   4. Expectation of a function of a random variable (4.4)
   5. Variance (4.5)
   6. The Bernoulli and Binomial random variables (4.6)
   7. The Poisson random variable (4.7)
   8. Geometric random variable (4.8.1)
   9. Properties of the Cumulative Distribution Function (4.9)
   10. Summary after the Chapter to be used for review
5. Continuous Random Variables
   1. Introduction: concept of probability density (5.1)
   2. Expectation and Variance (5.2)
   3. Uniform random variables (5.3)
   4. Normal random variables (5.4)
   5. The normal approximation of the binomial distribution; "0.5 correction" (5.4.1)
   6. Exponential random variables (5.5); skip 5.5.1 and 5.6
   7. Distribution of a function of a random variable (5.7: Example 7a, problem 5.40)
6. Jointly distributed random variables
   1. Joint distribution functions (6.1)
   2. Independent random variables (6.2)
   3. Distributions of sums of independent random variables (6.3)
7. Properties of expectation
   1. Expectations of sums (7.2)
   2. Covariance, variance of sums (7.4)
8. Limit theorems
   1. The central limit theorem. Approximation of sums of independent identically distributed random variables using the normal curve (8.3)

Key concepts

• Basic principle of counting, permutations, combinations, binomial theorem
• Sample space, outcomes, events. Probability as a function of event
• Classical definition of probability
• Conditional probability, independence
• Bayes' formula
• Discrete random variables, probability mass functions, cumulative distribution functions
• Expectation, variance in the discrete case
• Formula for the expectation of a function (w/o proof)
• Continous random variables, probability densities, cumulative distribution functions
• Expectation, variance; expectation of a function of a random variable
• Continuous probability distributions: uniform, normal, exponential, gamma
• Discrete probability distributions: Bernoulli, binomial, Poisson
• The DeMoivre-Laplace limit theorem and its use
• Joint distribution functions, densities. Marginal densities
• Independence of random variables. Equivalent definitions: product rules for probabilities, density functions and CDFs
• Convolution of density functions and the way to compute density for the sum
• Computing density for other combinations of random variables (XY, X/Y,...) using CDF
• Expectations, variances applied to the case of several random variables
• Covariance, variance of the sum formula
• The central limit theorem

Basic types of random variables

• Bernoulli
• Binomial
• Poisson
• Geometric
• Uniform
• Exponential
• Normal
• Gamma

List of theory questions

• Give the formulations of the three axioms of probability. Derive other properties of probability based on the axioms
• Derive formulas for the probability of a union of several events; prove Bonferroni's inequality for the intersection
• Compute expectations or variances for the random variables from the list above
• State the formal definition of conditional probability. Derive formulas of total probability (the rule of conditioning) and Bayes' rule from the definitions
• Derive a probability identity using conditional probability (see problems TH 1, 5, 25; ST 17, 21, 25 in Chapter 3)
• Verify a property of discrete random variables (see problems TH 10, 19, 27; ST 2, 5, 20 in Chapter 4)
• Verify a property of expectation, variance (see problems TH 7, 8, 18 in Chapter 5)
• Derive an expression for the density of a function of X, where X has known distribution (see problems TH 29, 30; ST 16 in Chapter 5)
• Derive the formula for the density of a sum of two independent random variables (Section 6.3)
• Show that the sum of two normal random variables has normal distribution (Section 6.3, Proposition 3.2)
• Show that the sum of two gamma random variables has a gamma distribution (Section 6.3, Proposition 3.1)
• Show that the sum of two Poisson random variables has Poisson distribution (Section 6.3)
• Show that the sum of two binomial random variables has binomial distribution (Section 6.3)