Speaking of disciplines and normalization...

Loet Leydesdorff loet at LEYDESDORFF.NET
Wed Oct 22 14:45:37 EDT 2008

Dear Christina, 
Thank you for noting this to the list. These authors use the 172 ISI Subject
Categories as an example, but their claim seems that however one divides the
total set into fields, rescaling to the mean for each subset does the job of
making results comparable because of the shape of the citation
The mathematicians among us are probably able to prove this. 
Best wishes, 

Loet Leydesdorff 
Amsterdam School of Communications Research (ASCoR), 
Kloveniersburgwal 48, 1012 CX Amsterdam. 
Tel.: +31-20- 525 6598; fax: +31-20- 525 3681 
 <mailto:loet at leydesdorff.net> loet at leydesdorff.net ;
<http://www.leydesdorff.net/> http://www.leydesdorff.net/ 



From: ASIS&T Special Interest Group on Metrics
[mailto:SIGMETRICS at LISTSERV.UTK.EDU] On Behalf Of Pikas, Christina K.
Sent: Wednesday, October 22, 2008 5:07 PM
Subject: [SIGMETRICS] Speaking of disciplines and normalization...

See this news piece in Nature?
Published online 20 October 2008 | Nature | doi:10.1038/news.2008.1169
Is physics better than biology?
Citation statistics now comparable across disciplines.
Philip Ball
Is the physics department at your university performing better than the
biology department? Answering such questions objectively has been hard,
because citation statistics and other bibliometric indicators can't be
directly compared across disciplines. But now a team in Italy has found a
way to do just that......

The full article isn't available at PNAS yet, but I *think* this ArXiv paper
is the pre-print. Offered without commentary - I'll let you all react with
shock and dismay (unless this has already appeared here, in which case,
oops!)  :)

Universality of citation distributions: towards an objective measure of
scientific impact
Authors: Filippo Radicchi, Santo Fortunato, Claudio Castellano
(Submitted on 5 Jun 2008)

    Abstract: We study the distributions of citations received by a single
publication within several disciplines, spanning all fields of science. We
show that the probability that a paper is cited $c$ times has large
variations between different disciplines, but all distributions are rescaled
on a universal curve when the relative indicator $c/c_0$ is considered,
where $c_0$ is the average number of citations per paper for the discipline.
In addition we show that the same universal behavior occurs when citation
distributions of papers published in the same field, but in different years,
are compared. These findings provide a strong validation of $c/c_0$ as an
unbiased indicator for citation performance across disciplines and years.
Based on this indicator, we introduce a generalization of the h-index
suitable for comparing scientists working in different fields. 

Comments:  14 pages, 5 figures
Subjects:  Physics and Society (physics.soc-ph); Data Analysis, Statistics
and Probability (physics.data-an)
Cite as:  arXiv:0806.0974v1 [physics.soc-ph]


Christina K. Pikas, MLS 
R.E. Gibson Library & Information Center
The Johns Hopkins University Applied Physics Laboratory 
Voice  240.228.4812 (Washington), 443.778.4812 (Baltimore) 
Fax 443.778.5353 

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