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CMB data help
 
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Zhao Wen



Joined: 20 Mar 2005
Posts: 5
Affiliation: USTC Hefei China

PostPosted: February 08 2008  Reply with quote

Dear friends:
Who can explain the meaning of binned data of CMB power spectra? How to get the binned data (mean value and the error bar) from the unbinned data? or introduce a paper for me? Thanks a lot!
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Sarah Bridle



Joined: 24 Sep 2004
Posts: 149
Affiliation: University College London (UCL)

PostPosted: February 08 2008  Reply with quote

I thought the binned data was just the weighted mean of the unbinned data (with the weighted mean error bar)? It certainly makes for a sensible looking plot..
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Zhao Wen



Joined: 20 Mar 2005
Posts: 5
Affiliation: USTC Hefei China

PostPosted: February 08 2008  Reply with quote

Thank you very much! But, as we known, in the bined data, the error bar is much smaller than the unbined data. If is only the weighted mean, the error bar of binned data can not be obtained.

Sarah Bridle wrote:
I thought the binned data was just the weighted mean of the unbinned data (with the weighted mean error bar)? It certainly makes for a sensible looking plot..
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Anze Slosar



Joined: 24 Sep 2004
Posts: 205
Affiliation: Brookhaven National Laboratory

PostPosted: February 09 2008  Reply with quote

Zhao Wen wrote:
Thank you very much! But, as we known, in the bined data, the error bar is much smaller than the unbined data. If is only the weighted mean, the error bar of binned data can not be obtained.

Sarah Bridle wrote:
I thought the binned data was just the weighted mean of the unbinned data (with the weighted mean error bar)? It certainly makes for a sensible looking plot..

If you add 1/σ2 it should probably be good enough for most purposes...., i.e. 1/σbinned2 = 1/σi2
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Zhao Wen



Joined: 20 Mar 2005
Posts: 5
Affiliation: USTC Hefei China

PostPosted: February 13 2008  Reply with quote

Thank you very much! I have known it!



Anze Slosar wrote:
Zhao Wen wrote:
Thank you very much! But, as we known, in the bined data, the error bar is much smaller than the unbined data. If is only the weighted mean, the error bar of binned data can not be obtained.

Sarah Bridle wrote:
I thought the binned data was just the weighted mean of the unbinned data (with the weighted mean error bar)? It certainly makes for a sensible looking plot..

If you add 1/σ2 it should probably be good enough for most purposes...., i.e. 1/σbinned2 = 1/σi2
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