Expectance and variance Flashcards
Understand expectance and variance
1
Q
What is E(x)?
A
The expected value for the Mean of x
2
Q
How is E(x) calculated?
A
It is the sum of the value of x times the probability of that value of x occurring
3
Q
What is Var(x)?
A
The variance across the values of x
4
Q
How is Var(x) calculated?
A
Either:
-Var(x)=E((x-E(x))^2)
or
-Var(x)=E(x^2)-(E(x^2))^2
5
Q
What is the expectance of x for the binomial distribution given by?
A
E(X)=np
where:
n-number of trials
p-probability of trials being successful
6
Q
What is the variance of x for the binomial distribution given by?
A
Var(X)=np(1-p)
