# TI-83 Discrete Random Variables ```TI-83 Discrete Random Variables
Suppose that x ( L1 ) is the number of pets owned by a
family and P(x) ( L2 ) 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x . Therefore,
highlight L3 and enter L1 * L2 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
L3 . Press 2nd QUIT to go back to the home screen.
Now press 2nd LIST and you should see the following
display.
Key over to MATH and down to 5: sum( as seen here
and press ENTER.
Enclose L3 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x    2 to calculate the standard
2
deviation. Begin by creating L4 with L1 * L2 as seen
to the right.
After pressing ENTER L4 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.
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