Statistics 12-7
8312STAT.DOC TI-83 international English Bob Fedorisko Revised: 02/19/01 12:42 PM Printed: 02/19/01 1:37
PM Page 7 of 38
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-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: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.