Texas Instruments 83CML/ILI/U Guidebook - Page 207

are adjusted automatically, and

Page 207 highlights

The residual pattern indicates a curvature associated with this data set for which the linear model did not account. The residual plot emphasizes a downward curvature, so a model that curves down with the data would be more accurate. Perhaps a function such as square root would fit. Try a power regression to fit a function of the form y = a ä xb. 22. Press o to display the Y= editor. Press ' to clear the linear regression equation from Y1. Press } Í to turn on plot 1. Press ~ Í to turn off plot 2. 23. Press q 9 to select 9:ZoomStat from the ZOOM menu. The window variables are adjusted automatically, and the original scatter plot of time-versuslength data (plot 1) is displayed. 24. Press ... ~ ƒ [A] to select A:PwrReg from the STAT CALC menu. PwrReg is pasted to the home screen. Press y [L1] ¢ y [L2] ¢. Press  ~ 1 to display the VARS Y.VARS FUNCTION secondary menu, and then press 1 to select 1:Y1. L1, L2, and Y1 are pasted to the home screen as arguments to PwrReg. 25. Press Í to calculate the power regression. Values for a and b are displayed on the home screen. The power regression equation is stored in Y1. Residuals are calculated and stored automatically in the list name RESID. 26. Press s. The regression line and the scatter plot are displayed. Statistics 12-7

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Statistics
12-7
The residual pattern indicates a curvature associated with this data set for
which the linear model did not account. The residual plot emphasizes a
downward curvature, so a model that curves down with the data would be
more accurate. Perhaps a function such as square root would fit. Try a power
regression to fit a function of the form y = a
ä
x
b
.
22. Press
o
to display the
Y=
editor.
Press
to clear the linear regression
equation from
Y
1
. Press
}
Í
to turn
on plot 1. Press
~
Í
to turn off plot
2.
23. Press
q
9
to select
9:ZoomStat
from
the
ZOOM
menu. The window variables
are adjusted automatically, and the
original scatter plot of time-versus-
length data (plot 1) is displayed.
24. Press
~
ƒ
[
A
] to select
A:PwrReg
from the
STAT CALC
menu.
PwrReg
is pasted to the home screen.
Press
y
[
L1
]
¢
y
[
L2
]
¢
. Press
±
~
1
to display the
VARS Y
.
VARS
FUNCTION
secondary menu, and then
press
1
to select
1:Y
1
.
L
1
,
L
2
, and
Y
1
are
pasted to the home screen as arguments
to
PwrReg
.
25. Press
Í
to calculate the power
regression. Values for
a
and
b
are
displayed on the home screen. The
power regression equation is stored in
Y
1
. Residuals are calculated and stored
automatically in the list name
RESID
.
26. Press
s
. The regression line and the
scatter plot are displayed.