1,045 research outputs found
On the calculation of percentile-based bibliometric indicators
A percentile-based bibliometric indicator is an indicator that values
publications based on their position within the citation distribution of their
field. The most straightforward percentile-based indicator is the proportion of
frequently cited publications, for instance the proportion of publications that
belong to the top 10% most frequently cited of their field. Recently, more
complex percentile-based indicators were proposed. A difficulty in the
calculation of percentile-based indicators is caused by the discrete nature of
citation distributions combined with the presence of many publications with the
same number of citations. We introduce an approach to calculating
percentile-based indicators that deals with this difficulty in a more
satisfactory way than earlier approaches suggested in the literature. We show
in a formal mathematical framework that our approach leads to indicators that
do not suffer from biases in favor of or against particular fields of science
The substantive and practical significance of citation impact differences between institutions: Guidelines for the analysis of percentiles using effect sizes and confidence intervals
In our chapter we address the statistical analysis of percentiles: How should
the citation impact of institutions be compared? In educational and
psychological testing, percentiles are already used widely as a standard to
evaluate an individual's test scores - intelligence tests for example - by
comparing them with the percentiles of a calibrated sample. Percentiles, or
percentile rank classes, are also a very suitable method for bibliometrics to
normalize citations of publications in terms of the subject category and the
publication year and, unlike the mean-based indicators (the relative citation
rates), percentiles are scarcely affected by skewed distributions of citations.
The percentile of a certain publication provides information about the citation
impact this publication has achieved in comparison to other similar
publications in the same subject category and publication year. Analyses of
percentiles, however, have not always been presented in the most effective and
meaningful way. New APA guidelines (American Psychological Association, 2010)
suggest a lesser emphasis on significance tests and a greater emphasis on the
substantive and practical significance of findings. Drawing on work by Cumming
(2012) we show how examinations of effect sizes (e.g. Cohen's d statistic) and
confidence intervals can lead to a clear understanding of citation impact
differences
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