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 Q3-Q1, where Q3 is the third quartile (75%) and Q1 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 Q1, Q3, 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
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. Q1 is listed as Q1X (in our example, Q1X=2). Q3 is listed as Q3X (Q3X=8.5). To find the IQR, subtract Q1 from Q3 on the Home screen. The IQR is 8.5-2=6.5.
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/