skewed citation distributions should not be averaged

[Glanzel, Wolfgang]

Dear Colleagues,

Please, read the text of 2.7 Myth #7 carefully. It is not about the distribution itself but about the distribution of the mean value. Furthermore, the text is not a statement but based on a proven theorem in probability theorem. One needs large however not huge data sets for empirical application.
I would also like to stress that the mean value is still an efficient and unbiased estimator of the expected value of the underlying random variable. This applies to all (continuous, discrete, symmetrical, skewed or whatsoever) distributions  as long as the latter one is finite. 
Best regards,

Wolfgang
-----Original Message-----
From: ASIS&T Special Interest Group on Metrics [mailto:SIGMETRICS at LISTSERV.UTK.EDU] On Behalf Of Sylvan Katz
Sent: Mittwoch, 31. August 2011 23:24
To: SIGMETRICS at LISTSERV.UTK.EDU
Subject: Re: [SIGMETRICS] skewed citation distributions should not be averaged


Loet,

Yes - perhaps something in the order of 20-30 years of Scopus or WoS data might be large enough.

Sylvan


--On Wednesday, August 31, 2011 11:08 PM +0200 Loet Leydesdorff <loet at LEYDESDORFF.NET> wrote:

> Adminstrative info for SIGMETRICS (for example unsubscribe):
> http://web.utk.edu/~gwhitney/sigmetrics.html
>
>> A closer look at the evolution of the citation distributions over a 
>> long
> period of time maybe necessary before a definitive answer can be given 
> to the question of whether "Citation distributions are so skewed that 
> using the mean or any other central tendency measure is ill-advised."
>
> Dear Silvan,
>
> Wouldn't one need very large samples (N > 10^6) to test this?
> Typically, IFs, for example, are computed over 10^2 - 10^3 citable items.
>
> Best,
> Loet
>



Dr. J. Sylvan Katz, Visiting Fellow
SPRU, University of Sussex
http://www.sussex.ac.uk/Users/sylvank