Fitter malfunctioning?
 

Hello--

I attempted to plot a trendline as a new data set (I looked at the fit
equation and created a new set of data with it). However, the line the
equation draws is not the same as the trendline! Am I making a mistake
somewhere?

The black line is the trendline. The blue line is the line the
equation describes.

Thanks,
Jennifer


For the Y column I'm using:
=(0.0000000009*(J2^3)) - (0.000004*(J2^2)) + (0.0057*J2) + 0.3246

Col J Col K
X Y
20 0.4370072
30 0.4920243
40 0.5462576
50 0.5997125
60 0.6523944
70 0.7043087
80 0.7554608
90 0.8058561
100 0.8555
110 0.9043979
120 0.9525552
130 0.9999773
140 1.0466696
...and so on...

Output:
[image: http://general.krl.caltech.edu/~jenant/fitter.jpg]


--
itgoeson
------------------------------------------------------------------------
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Jennifer -

Notice that the first two coefficients display only one significant
digit each. This is plenty of room to introduce error into the fitted
formula.

Select the trendline formula, press the Ctrl-1 (numeral one) shortcut to
the formatting dialog, and on the Number tab, choose a Scientific format
with 15 digits. This will provide a much closer fit than your earlier
attempt.

- Jon
-------
Jon Peltier, Microsoft Excel MVP
Peltier Technical Services
Tutorials and Custom Solutions
http://PeltierTech.com/
_______


itgoeson wrote:
Hello--

I attempted to plot a trendline as a new data set (I looked at the fit
equation and created a new set of data with it). However, the line the
equation draws is not the same as the trendline! Am I making a mistake
somewhere?

The black line is the trendline. The blue line is the line the
equation describes.

Thanks,
Jennifer


For the Y column I'm using:
=(0.0000000009*(J2^3)) - (0.000004*(J2^2)) + (0.0057*J2) + 0.3246

Col J Col K
X Y
20 0.4370072
30 0.4920243
40 0.5462576
50 0.5997125
60 0.6523944
70 0.7043087
80 0.7554608
90 0.8058561
100 0.8555
110 0.9043979
120 0.9525552
130 0.9999773
140 1.0466696
..and so on...

Output:
[image: http://general.krl.caltech.edu/~jenant/fitter.jpg]

Ahhhh thank you!


--
itgoeson
------------------------------------------------------------------------
itgoeson's Profile: http://www.excelforum.com/member.php...o&userid=25793
View this thread: http://www.excelforum.com/showthread...hreadid=392368