I3: A Non-Parametric Alternative to the Journal Impact Factor
We applied the integrated impact indicator (I3) to more than 10,000 journals and compared the results with other journal metrics. I3 provides a non-parametric statistic combining the measurement of impact in terms of citations (c) and performance in terms of publications (p) into a single metric. We argue for weighting using four percentile classes: the top-1 top-10 indicators. Unlike the h-index, which also appreciates both c and p, I3 correlates significantly with both the total number of citations and publications. I3 and h-index are size-dependent, division of I3 by the number of publications (I3/N) provides a size-independent indicator which correlates strongly with (the standard two-year) impact factor (JIF2) and JIF5 (JIF based on five publication years). The values of I3 and I3/N can be statistically tested against the expectation or one another using chi-square tests or effect sizes. Thus, one can indicate both performance and impact with a single number. We provide a template (in Excel) online for relevant tests.
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