Abstract
Although bibliometrics has been a separate research field for many years, there is still no uniformity in the way bibliometric analyses are applied to individual researchers. Therefore, this study aims to set up proposals how to evaluate individual researchers working in the natural and life sciences. 2005 saw the introduction of the h index, which gives information about a researcher’s productivity and the impact of his or her publications in a single number (h is the number of publications with at least h citations); however, it is not possible to cover the multidimensional complexity of research performance and to undertake inter-personal comparisons with this number. This study therefore includes recommendations for a set of indicators to be used for evaluating researchers. Our proposals relate to the selection of data on which an evaluation is based, the analysis of the data and the presentation of the results.
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Notes
The results of studies on citing behaviour “suggest that not only the content of scientific work, but also other, in part non-scientific, factors play a role in citing behaviour. Citations can therefore be viewed as a complex, multidimensional and not a unidimensional phenomenon” (Bornmann and Daniel 2008, p. 69). According to van Raan (2005a) “there is, however, sufficient evidence that these reference motives are not so different or ‘randomly given’ to such an extent that the phenomenon of citation would lose its role as a reliable measure of impact” (p. 135). A prerequisite is that the publication set of the researcher is sufficiently large.
Publications and citations are linked to scientific practice to varying degrees; otherwise, we could not have salami-slicing or salami style of publishing (Bornmann and Daniel 2007a). Scientists have been found to slice up data and interpretations into two, three, four, or more papers.
As an alternative to the NJP, other methods for normalizing the JIF could be used. An overview of these methods can be found in Vinkler (2010, pp. 186–189). For example, an interesting alternative is the %Q1 indicator. It is the ratio of publications that a researcher has published in the most influential journals. These journals are ranked in the first quartile (25 %) of their subject categories. It is an advantage of this indicator that an expected values is available: One can expect that 25 % of a researcher's publications have been published in the first quartile.
It might be a disadvantage of all normalizing methods that they are based on journal sets to delineate different fields. It is well known that these categories can be quite imprecise—especially in case of multi-disciplinary journals and highly specialized fields of research (Bornmann et al. 2008). Thus, if a publication list contains publications from these journals and/or the evaluated scientist is active in a highly specialized field, the use of journal metrics based on journal sets may be a problem.
Citations are a probabilistic process and therefore the number of citations to the publications of the researchers may vary for all sorts of reasons that have nothing to do with cognitive impact (Bornmann and Daniel 2008). In addition, the measurement of citations does inevitably entail measurement errors. Hence, statistical estimations of the possible error involved—like confidence intervals (Cumming 2012) or stability intervals (Waltman et al. 2012b)—around the values of citation indicators could be calculated and added.
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Bornmann, L., Marx, W. How to evaluate individual researchers working in the natural and life sciences meaningfully? A proposal of methods based on percentiles of citations. Scientometrics 98, 487–509 (2014). https://doi.org/10.1007/s11192-013-1161-y
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DOI: https://doi.org/10.1007/s11192-013-1161-y