1. Clear out all pre-existing data by hitting "AC" twice.
 
2. Enter the data; after each value, press the "data entry" key. This is the key which shows the summation symbol, which looks roughly like this:

-------
\         +
 \
 /
/
-------

For example, to enter the values 2,5,1 press: 2, data entry key, 5, data entry key, 1, data entry key.

3. For the mean, type [2nd], [STO]. (In this example, you should obtain the result 2.66...) For the standard deviation, use [2nd], [RCL]. The variance is obtained by squaring the standard deviation.

(Note: The TI-25 can also calculate the standard deviation using n instead of n-1, but we do not use that option.)