Graphing Residuals

(What is a residual?  See "Residuals and Least Squares".)

The graphing calculator uses a least squares regression equation to determine regression models.  When regression models are computed, residuals are automatically stored in a list called RESID.   
If you want to see the RESID list in the column list section of the calculator, you can place the values in L3 (for example).  Go to STAT and choose EDIT.  Place the cursor on the heading for L3.  Press LIST (2nd STAT) and choose #7 RESID.  Press ENTER.  The residual values are now in L3 for easy viewing.

Consider this set of data (which is “almost” a perfect linear equation)

If the data had been a perfect linear equation, you would have:

After adjusting the window, just hit GRAPH (not Zoom).