Suppose that x ( L
1
) is the number of pets owned by a family and P(x) ( L ) is the corresponding probability.
2
This represents a discrete probability distribution. Enter it as seen on the right.
Mean of a Discrete Probability Distribution
The mean is calculated by
    x

P
  
. Therefore, highlight L and enter
3
L
1
* L
2
as seen to the right.
Pressing ENTER will perform the calculation as can be seen here.
Now to calculate the mean we must sum the values in
L . Press 2
3 nd QUIT to go back to the home screen.
Now press 2 nd LIST and you should see the following display.

Key over to MATH and down to 5: sum( as seen here and press ENTER .
Enclose L in parentheses and press ENTER . This
3 gives you the mean of the Discrete Probability
Distribution.
Standard Deviation of a Discrete Probability Distribution
Use
    x
2 
P

 
2 to calculate the standard deviation. Begin by creating L with
4
L
1
2 to the right.
* L
2
as seen
After pressing ENTER L
4
will appear as follows.

Go back to the home screen and enter the command seen in the window to the right. Press ENTER and you will get the standard deviation.