Plotting Scatter Plots and Fitting Lines and Quadratics with the TI-89

by Steve Richardson

1.      Steps to enter ordered pairs and produce a scatter plot:

 Steps TI-89 Keystrokes 1.      Start the Data Matrix Editor a.       Type: Data b.      Folder: Main c.       Variable: (make up a name) APPS 6 3 2.      Enter the column of numbers under C1 3.      Enter the column of numbers under C2 4.      Display the Plot Setup Screen F2 5.      Define Plot 1 as: a.       Plot type = Scatter b.      Mark = Box c.       x = C1 d.      y = C2 F1 6.      Save the plot definition and return to Plot Setup screen ENTER   ENTER 7.      Display the Y= Editor F1 8.      Clear any pre-existing forumulae 9.      Use ZoomData to graph Plot 1 F2  9

2.      Steps to compute and display the line of best fit (this is called ‘linear regression’)

 Steps TI-89 Keystrokes 1.      Start the Data Matrix Editor on the ‘current’ data set APPS 6 1 (‘current’) 2.      Enter the Calc Menu: a.       Calculation Type: LinReg b.      x = C1 c.       y = C2 d.      Store RegEQ to: y1 F5 Item 5 ENTER 3.      Save Calc information ENTER 4.      Read the slope (a), intercept (b), correlation coefficient (corr) on the display.  Make a note of corr (i.e. write it down).  When done, press ENTER ENTER 5.      Display the Y= Editor F1 6.      Use ZoomData to graph Plot 1 F2  9

3.      Steps to compute and display the quadratic of best fit

 Steps TI-89 Keystrokes 7.      Start the Data Matrix Editor on the ‘current’ data set APPS 6 1 (‘current’) 8.      Enter the Calc Menu: a.       Calculation Type: QuadReg b.      x = C1 c.       y = C2 d.      Store RegEQ to: y1 F5 Item 9 ENTER 9.      Save Calc information ENTER 10.  Read the coefficients a, b and c.  Note .  When done, press ENTER ENTER 11.  Display the Y= Editor F1 12.  Use ZoomData to graph Plot 1 F2  9