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Topic: [ap-calculus] Re: logistic regression on the TI-86 (and TI-89)
Replies: 0

 Paul A. Foerster Posts: 892 Registered: 12/6/04
[ap-calculus] Re: logistic regression on the TI-86 (and TI-89)
Posted: Mar 27, 2001 7:23 PM

Drew and others who have been responding to this topic -

The problem is that logistic regression has what the fractals and chaos
people call "sensitive dependence on intial conditions." Try entering data
points that are well to the left of the point of inflection and doing
logistic regression. Then make a small change in the last data point. The
location of the upper horizontal asymptote can change by a factor of 2 to
10. What appears to be happening with the TI-86 that allows a vertical
shift as well as the other three constants seems to be related to this
sensitive dependence on initial conditions.

The moral of the story is, don't place too much reliance on predictions of
such things as the ultimate population of the United States based on
logistic regression. The usual cautions about extrapolation apply here,
too.

Regards, Paul

----------
From: Drew Isola <disola@accn.org>
To: "AP-Calculus" <ap-calculus@list.collegeboard.org>
Subject: [ap-calculus] Re: logistic regression on the TI-86 (and TI-89)
Date: Mon, Mar 26, 2001, 2:32 PM

I realize that the 86 regression equation allows for a vertical shift but
shouldn't the equation give values that are at least close to the 83
equation since they were generated from the same data?

Drew

Roger Keil wrote:
I agree with the comment about different solutions but not "errors". If you
look at the equations the TI 86 allows for a vertical shift that the 83 does
not take into consideration. It actually allows a more complete solution
then the 83. Also I believe the set of data you are using trys to take into
account the ln of "zero" which would cause the problem.

Roger Keil
North Hunterdon High School
Annandale NJ

Drew Isola wrote:
We got the same errors also, but we are only using 86's and 83's. This
happened when we tried to do #23 &24 on page 348 of FDWK, the same section
you cited.

Drew

Greg Kelly wrote:
We are using the TI-89, and the TI-89 never gets the same
regression equations as the book.
When finding the logistic regression equation for a set of data,
I sometimes get a message that says "Error: Singular Matrix". At
other times everything works fine, and I can't find a pattern as
to why it works sometimes and not others. Can anyone tell me
what is going on?

The data that I am having trouble with comes from the example
problem on page 345 of "Calculus: Graphical,Numeric, Algebraic"
by Finney, Demana, Waits & Kennedy. The TI-83 does the problem
successfully, but the TI-86 and TI-89will not. Interestingly
enough, the TI-89 will solve the problem if I leave off the first
data point.

This data produces the error:
L1:{0,10,20,30,40,50,60,70,80,90,100,110}
L2:{50.2,63,76,92,105.7,122.8,131.7,151.3,179.3,203.3,226.5,248.7}

Thanks,
Greg Kelly, Hanford High School, Richland, Washington

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