Texas Instruments TI-82 STATS 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
b
.
22. Press o to display the
Press ' to clear the linear regression
equation from
plot 1. Press ~ Í to turn off plot 2.
23. Press q
9
menu. The window variables are
ZOOM
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 press
FUNCTION
to select
1 1:Y
1
the home screen as arguments to
25. Press Í to calculate the power
regression. Values for
on the home screen. The power regression
equation is stored in
calculated and stored automatically in the
list name
RESID
26. Press s. The regression line and the
scatter plot are displayed.
editor.
Y=
. Press } Í to turn on
Y
1
to select
9:ZoomStat
] to select
A
STAT CALC
] ¢. Press 
L2
VARS Y.VARS
. , , and are pasted to
L L Y
1 2 1
and are displayed
a b
. Residuals are
Y
1
.
from the
menu.
.
PwrReg
Statistics 12–7