Solution 34925: Calculating Two-Variable Statistics on the TI-84 Plus Family of Graphing Calculators.
How do I calculate two-variable statistics on the TI-84 Plus family of graphing calculators?
Follow the example below to calculate two-variable statistics:
Data for this example:
• Press [STAT]  to access the STAT list editor.
• Enter the data in the L1 and L2 lists, making sure to press [ENTER] after each entry.
• Press [2ND] [QUIT] to return to the home screen.
Calculating the two-variable statistics:
• Press [STAT] [►]to highlight the CALC menu and press  to select the 2-Var Stats function.
• From here, the XList should be L1, the YList should be L2 and the FreqList should be blank. You can press [2ND] [L1] to obtain L1, and then [2ND] [L2] to obtain L2 if necessary.
• Press [ENTER] on "Calculate", and the two-variable statistics data will be displayed. The [▲] and [▼] keys can be used to scroll through the data.
Please see the TI-84 Plus Family guidebooks for additional information.