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 meaning of chiqsr/ dof number		  New Topic  Reply to Topic
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jule2013

Germany
3 Posts
Posted - 03/24/2013 :  06:07:30 AM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Ver. and Service Release (Select Help-->About Origin):
Operating System: Origin 7.0 (with Add-on for ITC)

Dear users,
I already searched this forum, but could not find the answer: I have done ITC measurements on a VP-ITC (GE healthcare) and the software supplied is an add-on for Origin 7.0 . I have tried to fit the data points to different models offered, like "binding on one site" or "sequential binding with x sites". Unfortunately the only measurement to judge the qualitity of fit that is offered is the chisqr/ dof . I always get things like 4E4 for the fit, but I have no clue if that is good or bad. When I checked the manual I found an example where they estimated a chisqr/ dof for the fit of 30000, so I guess it would be ok if I get 4E4? IT would be very kind if someone could explain this to me (also I'm not very good with statistics as it is quite some years ago that I had a class)?
Thanks!

matthew@originlab.com

73 Posts
Posted - 03/25/2013 :  09:24:48 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

Chi Sqr / DoF is also known as Reduced Chi Sqr. See if this thread answers your question: http://www.originlab.com/forum/topic.asp?TOPIC_ID=6819

Matthew
OriginLab
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jule2013

Germany
3 Posts
Posted - 03/25/2013 :  10:00:45 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Dear Matthew,

thanks for the quick reply, but the thread didn't help. I still don't know if a reduced chi sqr. in the order of 4E4 is good or bad?
Regards,
Jule
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matthew@originlab.com

73 Posts
Posted - 03/25/2013 :  12:50:00 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

A Reduced Chi Sqr value will ideally be close to 1. However, it can be scaled significantly with a scaling of y-data, so other measures such as R Sqr and Adjusted R Sqr can sometimes give a better indication of goodness of fit. See the following links for more information:

http://qhwiki.originlab.com/~originla/howto/index.php?title=QuickHelp:How_do_I_know_if_my_fit_result_is_good

http://qhwiki.originlab.com/~originla/howto/index.php?title=QuickHelp:Why_is_my_Reduced_Chi-Sqr_value_very_different_from_1

Matthew
OriginLab
Edited by - matthew@originlab.com on 03/25/2013 12:50:28 PM
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jule2013

Germany
3 Posts
Posted - 03/26/2013 :  05:46:35 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
The links really helped :)
Thanks a lot!
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