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Statistics 12-9
8312STAT.DOC TI-83 international English Bob Fedorisko Revised: 02/19/01 12:42 PM Printed: 02/19/01 1:37
PM Page 9 of 38
Now that you have a good model for the relationship between length and
period, you can use the model to predict the period for a given string length.
To predict the periods for a pendulum with string lengths of 20 cm and 50 cm,
continue with these steps.
30. Press
~
1 to display the
VARS
Y
.
VARS FUNCTION
secondary menu, and
then press
1 to select 1:Y
1
. Y
1
is pasted
to the home screen.
31. Press
£
20
¤
to enter a string length of
20 cm.
Press
Í
to calculate the predicted
time of about 0.92 seconds.
Based on the residual analysis, we would
expect the prediction of about 0.92
seconds to be within about 0.02 seconds
of the actual value.
32. Press
y
[
ENTRY
] to recall the Last Entry.
Press
|
|
|
5 to change the string
length to 50 cm.
33. Press
Í
to calculate the predicted
time of about 1.48 seconds.
Since a string length of 50 cm exceeds
the lengths in the data set, and since
residuals appear to be increasing as
string length increases, we would expect
more error with this estimate.
Note:
You also can make predictions using the table
with the
TABLE SETUP
settings
Indpnt:Ask
and
Depend:Auto
(Chapter 7).