QA Chapters 1 - 3

Question 1

Define conditional independence

Answer 1

P(A and B | C) = P(A|C) * P(B|C)

Question 2

Describe four common population moments

Answer 2

mu, sigma
skew measures asymmetry of a distribution
kurtosis measures size of tails, >3 means fat

Question 3

Distinguish key properties and identify common occurrences of the following distributions: uniform distribution, bernoulli distribution, binomial distribution, poisson distribution, normal distribution, lognormal distribution, Chi-squared distribution, Student’s t and F-distributions

Answer 3

Bernoulli:
E(x) = p
Var(X) = pq

Binomial
E(X) = np
Var(X) = npq

Poisson:
E(X) = Var(X) = lambda

Uniform:
E(X) = (a + b) /2
Var(X) = (b-a)^2 / 12

Independent normal distributions sum mu and sigma in resulting distribution

Lognormal:
E(X) = exp(mu + sigma^2/2)

Chi:
E(X) = v
Var(X) = 2v

F:
E(X) = v2 / (v2 - 2)