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Suppose that x (

*L*

1

) is the number of pets owned by a family and P(x) (

*L*

2

) is the corresponding probability.

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*

3

and enter

*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*

3

. Press

**2 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*

3

in parentheses and press

**ENTER**

. This 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*

4 to the right.

with

*L*

1

2

*

*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.