# sample mean and variance

#### Jeonsah

##### New member
Hey guys, I am lost on how to calculate the sample mean/variance for this problem:

Plot the probability mass function of the sample mean of X1, ...,Xn, when
a) n = 2;
a) n = 3.

Assume that the probability mass function of the sample mean of X1,...,Xn is
P{X = 0} = .2, P{X = 1} = .3, P{X = 3} = .5

The answer in the back of the book is
E[sample mean] = 1.8
V[Sample mean] = 4.8/n

Any help is appreciated.

#### tkhunny

##### Moderator
Staff member
You must resort to the definition of the mean. Let's see what you get.