# Mean and Standard Deviation on a TI-82/83/84

Here's how to compute some basic statistics on your TI-82, TI-83, and TI-84 (also the "plus" models, e.g. "TI-83 Plus").  TI-83 and TI-84 differences are summarized here (there's are only few).

1. Press the [STAT] button. You should see this on your screen:
2. Notice that EDIT and 1: are highlighted. Press [1] or just [ENTER] to indicate you want to edit (i.e. enter) a list of numbers. Now your screen should look something like:   or:
3. Now you can enter your data in the first column (or any other column you pick) just as you would in a computer spreadsheet.
If there is a list of numbers in the first column (or whatever column you want to use), as in the first picture above, put the cursor in that column, then press [DEL] until the column is empty, as in the second picture above.
4. Now type in your list of numbers, pressing [ENTER]after each one. For instance, if your list of numbers is {1,3,4,5,7}, then when you are done, your screen should look like the first picture in step #2 above. [Note: You do not have to enter the numbers in order]
1. Check over your list and make sure you have typed it correctly. You can delete entries with the [DEL] key, or insert entries by using the [2nd][INS] keys. Note: To type [2nd][INS], press the [2nd] key, then find INS above the [DEL] key, and press that key.
5. Press the [STAT] button again, so that you are back to:
6. Press the   key to highlight the CALC heading, and the screen changes to:
7. Notice that CALC and 1: are highlighted. Press [1] or just [ENTER] to indicate you want to calculate some one-variable statistics for your list. The screen now looks like:
8. Now tell the calculator what list you put your numbers in. Normally this will be the list L1, but use whatever list you typed your numbers under in step #4. To type L1, press [2nd][L1]   (L1 is over the [1] button). You should now see:
9. Press [ENTER]to do the computation:

10. The =4 tells you the mean of your list is 4. The x=2 tells you the [population] standard deviation of your list is 2.

### Short summary:

Press [STAT] and select EDIT to enter your list of numbers. Remember the list you entered them in (watch the heading over your number on the calculator screen). Press [STAT] and select CALC, then select 1-Var Stats. Enter the name of the list you used, and press [ENTER] to view the results.

### Test yourself:

Try to get the mean and standard deviation of   37.75, 38, 37, 38.5, and 37.5. You should get a mean of 37.75 and a standard deviation of 0.5 (exactly 0.5).

## Bonus Topics:

### Frequency tables:

If you have many repeated data items, such as a frequency table:

 data item frequency 3 4 4 5 1 7 5 1

...meaning that your list contains four 3's, five 4's, seven 1's etc., then you can enter two lists of data (preferably in L1 and L2) as shown:

Then ask the calculator to calculate 1-variable statistics for L1 and L2 as shown:

### Help with medians:

TI-82 ('83 is simpler, see below): Once you type a list of numbers into a column in the list editor (see steps #1- #4 above), you can press [STAT] again, select SortA(, indicate L1 (or whatever list you put your numbers in) and press enter: . Then when
you edit the list again, you will find the list is displayed in ascending order, making it easier to pick out the median.

TI-83/84:  After you do the 1-Var Stats, just scroll down (with the down arrow) to see the median and some other statistics.