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

<Green Diamond> 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

<Green Diamond> 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

<Green Diamond> F1

12.  Use ZoomData to graph Plot 1

F2  9