Probability and Statistics Index > TI-89 statistics > Interquartile Range TI 89

## How to Find Q1, Q3 and the Interquartile Range TI 89

In order to calculate the IQR by hand, you would have to do a few separate calculations, including finding the mean. The interquartile range formula is Q_{3}-Q_{1}, where Q_{3} is the third quartile (75%) and Q_{1} is the first quartile (25%). You could use the online interquartile calculator found on this site. However, you can’t bring the internet to a test, and it’s easy to make errors when calculating by hand. That’s where the **TI-89 calculator** comes in handy.

## Interquartile range TI 89: Steps

Watch the video or read the steps below:

**Sample problem**: Find Q_{1}, Q_{3}, and the IQR for the following list of numbers: 1, 9, 2, 3, 7, 8, 9, 2.

**Step 1:** *Press * Apps*. Scroll to Stats/List Editor (use the arrow keys on the keypad to scroll). Press *Enter. If you don’t have the stats/list editor you can download it here.

**Step 2:** *Clear the list editor of data:* press F1 8.

**Step 3:*** Press* ALPHA 9 ALPHA 1 ENTER. This names your list “IQ.”

**Step 4:** *Enter your numbers, one at a time.* Follow each entry by pressing the ENTER *key.* For our group of numbers, enter

1,9,2,3,7,8,9,2

**Step 5:*** Press F4, then* ENTER (for the 1-var stats screen).

**Step 6:** *Tell the calculator you want stats for the list called “IQ” by entering *ALPHA 9 ALPHA 1 into the “List:” box. The calculator should automatically put the cursor there for you. Press ENTER twice.

**Step 7:***Read the results.* Q_{1} is listed as Q1X (in our example, Q1X=2). Q_{3} is listed as Q3X (Q3X=8.5). To find the IQR, subtract Q_{1} from Q_{3} on the Home screen. The IQR is 8.5-2=6.5.

*That’s it!*

Check out our YouTube channel for hundreds of elementary statistics how to videos!

Questions about interquartile range TI 89? Post your question on our free statistics help forum. One of our mods will be happy to help/