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 Weighting method to calculate errors		  New Topic  Reply to Topic
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a.abc.b35

175 Posts
Posted - 05/10/2011 :  10:47:03 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Ver. and Service Release (Select Help-->About Origin): 8.0 SR0
Operating System:Win 7
........
Hi there. I am using the weighing method to calculate errors of fit parameters during non linear curve fitting to my data.I have three columns, X, Y, Y_Error (Y_Error = sqrt(Y)) I found out that if I use the Y_Error column with the 'direct weighting' option, then I get reasonable values for the error bars instead of the instrumental error. I have read the documentation at [http://www.originlab.com/www/helponline/Origin/en/UserGuide/Fitting_with_Errors_and_Weighting.html]this address[/http://www.originlab.com/www/helponline/Origin/en/UserGuide/Fitting_with_Errors_and_Weighting.html] and also the origin help file but am not able to get a proper definition of this method. Can an expert help me out here please ?

AB

easwar

USA
1964 Posts
Posted - 05/12/2011 :  10:12:36 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi AB,

As the documentation page indicates, the direct weight assigns weights to the points by directly multiplying with the values in your error bar column. So points with larger error values get more weighting/importance in the fitting process, and the fit line will tend to go closer to those points.

The instrumental weight on the other hand uses the square of the reciprocal of the error values, so points with smaller error values will have more weight/importance.

As to which method is suitable for the data is really up to how you understand and interpret your data, and what is typical for analysis of such data in your field of work. We cannot recommend which weighting method you should use.

Hope this helps.

Easwar
OriginLab
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a.abc.b35

175 Posts
Posted - 05/12/2011 :  1:17:14 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Thanks Easwar for the reply. This helps. I am going to use the instrument error method. Thanks again.

AB
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rayka

Australia
1 Posts
Posted - 05/16/2011 :  03:32:52 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
hi AB.. we have the same matter here. i wanted to create a new topic but i found yours. thanks. will try this way.
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