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.
The formula for finding the standard deviation of these values is σ = √(Σx2P(x)-μ2)
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 x2
- Label the L4 column as L2*L3. This will give you x2P(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 Σx2P(x)
- 'Enter the equation sum(L5). Record this value as μ
- Enter the equation √(Σx2P(x)-μ2), substituting the variable with the previously recorded amounts
- The resulting value will be your standard deviation