Create your list of numbers, making sure to type them within braces on an empty calculator screen. The data should appear as {4,6,8,12,15,17,17}.
Store the numbers you've typed by hitting the "STO>" button, which is located in the bottom left corner of a TI-83 calculator, just above the "On" button. Name your list, usually with generic name such as L1, and hit "Enter," which is at the bottom right-hand corner.
Press the "STAT" button, located to the left of the "Left" button in the multidirectional pad under the screen, in the upper right. After the "STAT" screen is up, tab over to the "CALC" using the right arrow. Tab down one to "1-var stats" and press "Enter."
Sort through the list of data, assuming it gave you an output from the information you entered in Step 1. You should see minX (minimum X value), Q1 (lower quartile), Med (median), Q3 (upper quartile), and maxX (maximum X value).