Problem:
Given the following table:

Year:1980198119821983198419851986198719881989
DJ Average8249728821027125211981537192720152144
[Extracted from the Chance site.]

find and graph the least squares regression line.


Solution:
Using the TI-85 graphing calculator:


[Press here to see animation again!]

  1. Press the STAT key and then pick  EDIT  by pressing the F2 key.
  2. You can change the names for the list of values which you will be entering but it is not necessary. Press the ENTER key twice if do not change the names.
  3. To clear out previous data, pick  CLRxy  by pressing the F5 key.
  4. At the prompt  x1= , type in the first year as the first x-value: 1980 and press the ENTER key.
  5. At the prompt  y1= , type in the first DJ Average as the first y-value: 824 and press the ENTER key.
  6. Keep repeating this to enter all ten pairs of numbers. After you have entered the tenth pair, press the EXIT key.
  7. Pick  CALC  by pressing the F1 key.
  8. Press the ENTER key twice and you will be given the opportunity to choose a number of options including  LINR  choose this option by pressing the F2 key.
  9. You will see the following screen:

    This indicates that the equation of the least squares line is:

    y = -309912.072727 + 156.8606061 x

  10. Press the EXIT key followed by the DRAW key.
  11. If some previous graph appears on the screen then
  12. Most probably you will need to change to the bounds of the viewing screen to see all of the data points. To do this,
  13. Pick  SCAT  by pressing the F2 key to see the collection of data points:

  14. Pick  DRREG  by pressing the F4 key to draw the graph of the least squares line: