Your starting information should include the differant values of variable 'x' and the corresponding probabilities 'p(x)'. The sum of p(x) should equal 1.

Ex.

x | p(x) |

0 | .6 |

1 | .2 |

2 | .1 |

3 | .1 |

The formula for finding the standard deviation of these values is σ = √(Σx^{2}P(x)-μ^{2})

To enter this information into a graphing calculator, do the following:

- Go to STAT>EDIT>Edit
- Enter the values of x in the L1 column, and the values for p(x) in the L2 column
- Label the L3 column as L1^2. This will give you x
^{2} - Label the L4 column as L2*L3. This will give you x
^{2}P(x) - Label the L5 column as L1*L2. This will give you xP(x)
- Return to the home screen.
- Go to LIST(2nd-STAT)>MATH>sum(
- Enter the equation sum(L4)'. Record this value as Σx
^{2}P(x) - 'Enter the equation sum(L5). Record this value as μ
- Enter the equation √(Σx
^{2}P(x)-μ^{2}), substituting the variable with the previously recorded amounts - The resulting value will be your standard deviation

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