Texas Instruments TI-83 Manual Book page 207

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
22. Press o to display the
Press ' to clear the linear regression
equation from
on plot 1. Press ~ Í to turn off plot
2.
23. Press q
9
the menu. The window variables
ZOOM
are adjusted automatically, and the
original scatter plot of time-versus-
length data (plot 1) is displayed.
24. Press ... ~ ƒ [
from the
A:PwrReg
is pasted to the home screen.
PwrReg
Press y [ ] ¢ y [
L1
~
to display the
1
secondary menu, and then
FUNCTION
press to select
1
pasted to the home screen as arguments
to .
PwrReg
25. Press Í to calculate the power
regression. Values for
displayed on the home screen. The
power regression equation is stored in
. Residuals are calculated and stored
Y
1
automatically in the list name
26. Press s. The regression line and the
scatter plot are displayed.
editor.
Y=
. Press } Í to turn
Y
1
to select
9:ZoomStat
] to select
A
STAT CALC
] ¢. Press 
L2
VARS Y.VARS
. , , and
1:Y L L
1 1 2
and are
a b
RESID
b
.
from
menu.
are
Y
1
.
Statistics 12-7