  In recent years, the relationship of collaboration among scientists and the
citation impact of papers have been frequently investigated. Most of the
studies show that the two variables are closely related: an increasing
collaboration activity (measured in terms of number of authors, number of
affiliations, and number of countries) is associated with an increased citation
impact. However, it is not clear whether the increased citation impact is based
on the higher quality of papers which profit from more than one scientist
giving expert input or other (citation-specific) factors. Thus, the current
study addresses this question by using two comprehensive datasets with
publications (in the biomedical area) including quality assessments by experts
(F1000Prime member scores) and citation data for the publications. The study is
based on nearly 10,000 papers. Robust regression models are used to investigate
the relationship between number of authors, number of affiliations, and number
of countries, respectively, and citation impact - controlling for the papers'
quality (measured by F1000Prime expert ratings). The results point out that the
effect of collaboration activities on impact is largely independent of the
papers' quality. The citation advantage is apparently not quality-related;
citation specific factors (e.g. self-citations) seem to be important here.
