Texas Instruments TI-84 Plus Manual page 26

Press
ENTER .
the cursor opposite that list name and press
screen with
2ND
WARNING: Be careful when in the
from the calculator's memory and cannot be recovered. If you mistakenly delete one of the lists
you need to redo the statistical setup as indicated on page A-1 of this Guide.
L1, L2, ..., L6,
WHAT IS "BEST FIT"? It is important to understand the method of least squares and the
conditions necessary for its use if you intend to find the equation that best-fits a set of data.
You can explore the process of finding the line of best fit with program
calculator programs may be downloaded from the Calculus Concepts website:
http://college.hmco.com/mathematics/latorre/calculus_concepts/3e/students/programs.html.)
For your investigations of the least-squares process with this program, it is better to use data
that is not perfectly linear and data for which you do not know the best-fitting line.
We use the data in the table below to illustrate program LSLINE, but you may find it more
interesting to input some other data
x
(input in L1)
y
(output in L2)
Before using program
ening the name
Plot1
turned on, the program will not execute properly.) Next, draw a scatter plot with
. Press
[ZoomStat]
help identify points when you are asked to give the equation of a line to fit the data. (Four the
Guide illustration, we set
then return to the home screen.
To activate program
number corresponding to the location of the program, and press
The program first displays the scatter plot you
ENTER .
constructed and pauses for you to view the screen.
NOTE: While the program is calculating, there is a small vertical line in the upper-right hand
corner of the graphics screen that is dashed and "wiggly". This program pauses several times
during execution for you to view the screen. Whenever the program pauses, the small line is
"still" and you should press
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.)
3
This program works well with approximately 5 data points. Interesting data to use in this illustration are the height and
weight, the arm span length and the distance from the floor to the navel, or the age of the oldest child and the number of
years the children's parents have been married for 5 randomly selected persons.
26
To delete another list, use
when finished.
MODE (QUIT)
DELETE
3 .
1 3
1 6
, clear all functions from the
LSLINE
on the screen, and enter your data in lists
Y=
and reset
WINDOW Xscl
to 1 and
Xscl Yscl
, press
LSLINE PRGM
to resume execution after you have looked at the screen.
ENTER
or to move
▼ ▲
Exit this
ENTER .
menu. Once you delete something, it is gone
7
10 16
Y=
L1
and so that you can use the tick marks to
Yscl
to 5.) Press
GRAPH ,
followed by the
Copyright © Houghton Mifflin Company. All rights reserved.
Chapter 1
. (All TI
LSLINE
9 12
20
list, turn on by dark-
Plot1
and . (If is not
L2 Plot 1
ZOOM 9
view the scatter plot, and