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scalpa

France
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Posted - 12/09/2013 :  11:45:49 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin pro 9.0:

Hello,
i would like to compare the slopes of the linear fits of two different datasets. to be more accurate, I have two distinct data sets that I fit independently by a linear regression. I then get 2 slopes as results (I'm not interested in the intercepts) and I would like to know if these slopes are significantly different or not.

thanks !!

PSilberz

Sam Fang

293 Posts
Posted - 12/11/2013 :  9:05:32 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
It can be done as follows:
1. Perform Linear Fits for two data separately.
Compute the sum of two RSS(Residual Sum of Squares) and df(Degrees of Freedom), and they are denoted by RSS1, df1.
2. Share the two slopes and perform global linear fit for two data in NLFit dialog. RSS and df in the global fit are denoted by RSS2, df2.
3. Determine whether slopes are different. You can run following script in Origin's script window.

F1=(RSS2-RSS1)/(df2-df1)/(RSS1/df1);
p1=1-fcdf(F1,df2-df1,df1);


If p1<0.05, slopes are different.

We will provide a built-in tool to compare parameters in fitting in Origin's next version.

Sam
OriginLab Technical Services
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scalpa

France
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Posted - 12/12/2013 :  04:57:56 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Thanks a lot Sam,

How can I call this test if I am to describe it ?

best

scalpa
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Sam Fang

293 Posts
Posted - 12/12/2013 :  05:35:24 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
You can send your data to us, and then we can make an analysis template for you. The problem is not complex.

To send files to us, click Send File to Tech support button in the top right of the forum.

Thanks.



Sam
OriginLab Technical Services
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scalpa

France
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Posted - 12/12/2013 :  06:08:24 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
I think I was not clear: following your indications, the test allows me to conclude. but I would need some background (ie the name of the test via this f distribution function). thanks,
S.
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Sam Fang

293 Posts
Posted - 12/12/2013 :  9:04:21 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
The test is F-test. Origin's Compare Datasets tool also uses F-test.

Sam
OriginLab Technical Services
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