Texas Instruments TI-89 Manual page 35

TI-89 Guide
Press
ENTER
and it next tells you what the tick mark
settings are. After pressing
you see a graph of the scatter plot.
The program next asks you to find the y-intercept and slope of
some line you estimate will go "through" the data. (You should
not expect to guess the best-fit line on your first try!) Use the
tick marks to estimate rise divided by run and note a possible y-
intercept. Enter your guess for the slope and y-intercept.
After pressing
is drawn and the errors are shown as
vertical line segments on the graph.
Next the sum of squared errors,
displayed for your line.
Decide whether you want to move the y-intercept of the line up or down or change the slope of
the line to improve the fit to the data.
Press
ENTER
then shown the scatter plot to view. After deciding on a new
guess for the slope and/or y-intercept, press
new values when requested.
The process of viewing your line, the
errors, and display of
If the new value of
the for your first guess (as is the
SSE
case here), you have improved the fit.
When you are satisfied with your line,
enter at the
2 [no]
The program shows the linear fit calcu-
lation. Press
ENTER
best fit and your last line are drawn.
Press
ENTER
and its errors display. The
best-fit line is shown and then all the
parameters of the best-fit line are given.
Press to end the program
ENTER
8
squares that the TI-89 uses to find the line of best fit.
7
Program LSLINE is for illustration purposes only. Actually finding the line of best fit for a set of data should be done
according to the instructions in Section 1.5.7 of this Guide.
8
Two articles that further explain "best-fit" are H. Skala, "Will the Real Best Fit Curve Please Stand Up?" Classroom
Computer Capsule, The College Mathematics Journal, vol. 27, no. 3, May 1996 and Bradley Efron, "Computer-Intensive
Methods in Statistical Regression," SIAM Review, vol. 30, no. 3, September 1988.
Copyright © Houghton Mifflin Company. All rights reserved.
to continue the program
ENTER ,
again, your line
ENTER
, is
SSE
type to choose the
1 Try Again?
is repeated.
SSE
is smaller than
SSE
prompt.
Try Again?
and the line of
and the line of best fit
for the
SSE
Use program
.
option. You are
Input the
ENTER .
7
to explore the method of least
LSLINE
TI 89-35