Discrete random variables

Question 1

what is variance and standard deviation

Answer 1

variance is the square of the average distance of an item from the mean
standard deviation is the square root of variance

Question 2

ways to say mean of x

Answer 2

x bar, μ, E(x)

Question 3

Variance formulae

Answer 3

E(x-μ)^2
E(εx^2/n) - E(εx/n)^2
E(x^2) - E(x)^2
εxi^2pi - εxi^2pi^2

Question 4

xi and pi meaning

Answer 4

xi is possible value of x
pi is possibility of that value of x happening

Question 5

expectation of x formula

Answer 5

sum of xipi

Question 6

E(ax + b)

Answer 6

aE(x) + b

Question 7

Var (aX + b)

Answer 7

a^2 Var(x)
ignore b

Question 8

E(X1 + X2)
E(X1 - X2)

Answer 8

E(X1) + E(X2)
E(X1) - E(X2)

Question 9

Var(X1 + X2)
Var(X1 - X2)

Answer 9

Var(X1) + Var(X2)
same for both i.e -1 squared = 1