Discrete Random Variables

Question 0

How would you work out cumulative distribution?

f(x) = P(X<=x)

Answer 0

Adding up the probabilities before a certain values, specified in the P(X<=x)

Question 1

What is the meaning of ∑x*P(X=x) ?

Answer 1

It is the mean:

Score * Probability

Question 2

How would you deal with E(aX)?

Answer 2

aE(X)

Question 3

How would you deal with E(aX+b)?

Answer 3

aE(X) + b

Question 4

How would you deal with Var(aX)?

Answer 4

a^2 * Var(X)

Question 5

How would you deal with Var(aX + b)?

Answer 5

a^2 * Var(X)

Question 6

What is a simplified formula for Var(X)?

Answer 6

E(X^2) - [E(x)]^2

Question 7

What is discrete uniform distribution?

Answer 7

A variable X is defined over a set of n distinct values.
e.g. P(X=x) = 1/n for all values of x.

(Basically… When all probabilities are equally likely - the same.)