TI-83 Instructions

Computing a Sample Variance and Standard Deviation

Enter the data into List L1.

Method 1 (Standard Formula)

1. Compute the mean of L1.  (See Computing a Mean.)
2. Press L1.
3. Press (minus).
4. Enter the mean.
5. Press ENTER.  The display shows a list of deviations.
6. Press STO.
7. Press 2nd L2.
8. Press ENTER.  The deviations are now stored in list L2.
9. Enter the expression sum(L2^2).
10. Press ENTER.  The display now shows the sum of the squared deviations, i.e., SS(x).
11. Press ÷ (divide).
12. Enter one less than the sample size, i.e., n – 1.
13. Press ENTER.  This gives the variance.
14. Press 2nd (square root).  The symbols √( appear.
15. Press 2nd ANS.  The expression Ans appears after the square root.  This refers to the result of the previous calculation, which in this case is the variance.
16. Press ).
17. Press ENTER.  The display now shows the standard deviation.

Method 2 (Alternative Formula)

1. Enter the expression sum(L1^2) – sum(L1)^2.
2. Press ÷ (divide).
3. Enter the sample size.
4. Press ENTER.
5. The display now shows the sum of the squared deviations, i.e., SS(x).  From here on, follow steps 11 – 17 under Method 1.

### Method 3

1. Press STAT.
2. Select the CALC menu title.
3. Select the first item, 1-Var Stats.
4. Press ENTER.  The phrase 1-Var Stats appears in the display.
5. Press 2nd L1.
6. Press ENTER.  A list of statistics appears.  The fourth one in the list, Sx, is the sample standard deviation.  (Be careful not to use σx.  It represents the population standard deviation.)