The Steps to a Linear Regression on the TI-89 page produced a linear regression, a plot of the data points, and a plot of the regression line. It did this without the use of some special features of the TI-89. This page will perform a similar analysis of the same data, but this time we will use the List Editor and other special features of the TI-89.
In the text we are given the following table
x (miles) | 3 | 5 | 9 | 11 | 12 | 15 | 20 | 25 |
y (time) | 6 | 9 | 13 | 16 | 16 | 21 | 28 | 31 |
![]() | We will start by entering the data into the calculator. To do this we will
use the List Editor. We open the List Editor by first
pressing the ![]()
Of the options presented, we are interested in #6, Data/Matrix Editor.
We can press the |
![]() | The TI-89 responds by asking if we want to edit the current item,
open an existing item, or create a new item. This is a new problem.
Therefore, we press ![]() |
![]() | To define a new item, the TI-89 needs more information.
Figure 3 shows the screen that the calculator uses to obtain that
information. The default is to have the new item be of type Data.
This is not what we want. Therefore we press the |
![]() | In Figure 4 we see a new window, one that allows us to choose the type
of data that we want. In our case we want a list of values.
We press ![]() |
![]() | The calculator returns to the previous screen,
having changed Data to List
in the Type line.
Because we will create the new list in the main folder,
we will leave the second line as it is. We use the
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
![]() | In Figure 6 we finally see the List Editor.
We are ready to start entering the data from our two lists.
Note that the calculator is still in alphabetic mode.
We will have to press the ![]() |
![]() | Figure 7 captures the screen after we have entered the first 3 values from our miles list, and in the middle of the entry of the fourth value, 11, which is in the data and command entry line. |
![]() | In Figure 8 we have finished entering the eight values for the
first list, miles, and we have used the
![]() |
![]() | As of Figure 9 we have entered all of the values into
our two columns. The List Editor makes it easy for us to enter the data,
to check the data, and to verify that corresponding values from the
two lists are on the same row of data.
At this point we are ready to set up the plot area. To do this we press
|
![]() | The result is the window shown in Figure 10. Actually, we do not want to be
here.
Rather thn set up the plot, we want to specify the
kind of data analysis that is to be performed.
We really want to return to the previous window, shown in Figure 9, and
from there select the Calc tab. To do this we press
![]() ![]() |
![]() | Figrue 11 shows the "Calculate" screen.
The default "Calculation Type" is TwoVar.
We want to alter that selection. Therefore,
we press ![]() |
![]() | Now we have some choices for the Calculation Type.
In particular, item 5 is the LinReg or Linear Regression option.
We select taht option by pressing ![]() |
![]() | In Figure 13 we can verify that the Calculation Type has been changed to LinReg. In addition, we have specified that the x list is in c1 and the y list is in c2. Those were the column names that we saw back in Figures 6 through 9. |
![]() | We use the ![]() ![]() |
![]() | The new window in Figure 15 gives the alternate values for the
![]() ![]() |
![]() | Again, the change is reflected in the Calculate window.
We press ![]() |
![]() | Figure 17 shows the window that pops
up to give us the results of the computation.
This STAT VARS window is identical to that produced
in Figure 13 of the other web page,
Steps to a Linear Regression on the TI-89,
which used a different approach to doing this same problem.
We can close the STAT VARS window and return to the List Editor
by pressing the |
![]() | Leaving Figure 17 would return us to the image captured in
Figure 9. Now we do want to set up a plot. Again, we do this by pressing
![]() |
![]() |
We will define Plot1 by pressing ![]() |
![]() | The window shown in Figure 19 allows us to define Plot 1.
The default is a Scatter plot, and that is what we want.
We will be happy to use a small Box as a marker of the
location of the data points on the plot.
We need to specify the x list and the y list.
We use the ![]() |
![]() | In Figure 20 we have identified the x list as the valuse
in column c1, and the y list as the values in column c2.
We can press ![]() ![]() |
![]() | Here we can see that the definition of Plot1 has changed to
indicate that we want a Scatter plot, using the small Box as a
marker, with the x list as c1 and the y list as c2.
|
![]() | We can move to view the plot and the graph of the Regression Equation
by pressing ![]() ![]() The result shown in Figure 22 depends upon the calculator WINDOW settings being the standard settings, 10 to 10 for both x and y. With those settings we can see the regression equation, but only two of the data points. The third point has an x value of 9 which could be graphed, but the y value is 13 which is off the window. |
![]() | It is pretty clear that we want to see more of the
data points. We can press ![]() ![]() ![]() |
![]() | The resulting new graph, shown in Figure 24,
has had its WINDOW settings changes to accommodate all of the data points.
Unfortunately, that means that the y-axis is no longer visible,
and, the x-axis, which seems to be on the image, is not really the x-axis.
We can press ![]() ![]() |
![]() | The values displayed in Figure 25 are those set by the calculator when we used the ZoomData command. We will want to change those values so that they conform to the values used inthe text. |
![]() | Once the new values are set, we can press
![]() ![]() |
![]() | Finally, we have a graph similar to the one generated for the
text. The beauty of using the built-in special functions of the TI-89 is that we can change data values and produce new results with relative ease. For example, if we want to change the final data pair from (25,31) to (25,39), we can perform the follwoing steps. |
![]() | Open the APPS menu via ![]() ![]() ![]() |
![]() | In the List Editor, move to row 8 column 2 and change the
value there from 31 to 39. Press the ![]()
Then, press |
![]() | The calculator presents the Calculate window. |
![]() | Fill in the Calculate window as before.
Press ![]() |
![]() | Read the values from the STAT VARS window.
Press ![]() ![]() ![]() |
![]() | The data points have been plotted again. Because there has been a change in a data point, the regression equation has changed. |
PRECALCULUS: College Algebra and Trigonometry
© 2000 Dennis Bila, James Egan, Roger Palay