Expectance and variance

Question 1

What is E(x)?

Answer 1

The expected value for the Mean of x

Question 2

How is E(x) calculated?

Answer 2

It is the sum of the value of x times the probability of that value of x occurring

Question 3

What is Var(x)?

Answer 3

The variance across the values of x

Question 4

How is Var(x) calculated?

Answer 4

Either:
-Var(x)=E((x-E(x))^2)
or
-Var(x)=E(x^2)-(E(x^2))^2

Question 5

What is the expectance of x for the binomial distribution given by?

Answer 5

E(X)=np
where:
n-number of trials
p-probability of trials being successful

Question 6

What is the variance of x for the binomial distribution given by?

Answer 6

Var(X)=np(1-p)