Re: Citation analysis of author-choice OA journals

[Phil Davis <pmd8@cornell.edu>]

Stevan,

Our study focuses on estimating the effect of author-choice open 
access on article citations. The 11 journals were selected 
because they gathered sufficient paying open access submissions 
as to make a statistical analysis even potentially possible. 
Still, if the open access effect is small, a larger sample size 
is required to detect a signal amongst the noise, which is why I 
aggregated the 11 journals for subsequent analyses. PNAS 
contributed so many articles in the aggregate dataset (about a 
third) that I didn't want this one journal to skew the results, 
hence the tables report the analyses with and without PNAS.

Secondly, while aggregating the journals resulted in increased 
statistical power, we are combining articles published in 
*different* scientific fields (biology, medicine, bioinformatics, 
plant sciences, and multi-disciplinary sciences), which is why 
journal impact factors are not used as an explanatory variable. 
Please note that I did include the variable Journal as either a 
random variable (Table 2) or a fixed variable (Table S2), so 
journal-to-journal variation is being accounted for in the model

While I appreciate your routine post-acceptance advice on 
methodological improvements, I encourage you to embark on similar 
analyses that address your own personal research interests. The 
data are all public.

Phil Davis

Stevan Harnad wrote:
> Confirmation Bias and the Open Access Advantage:
> Some Methodological Suggestions for Davis's Citation Study
>
> Stevan Harnad
>
> Full text: http://openaccess.eprints.org/index.php?/archives/451-guid.htm