How to analyse percentile impact data meaningfully in bibliometrics: The   statistical analysis of distributions, percentile rank classes and top-cited   papers
  According to current research in bibliometrics, percentiles (or percentile rank classes) are the most suitable method for normalising the citation counts of individual publications in terms of the subject area, the document type and the publication year. Up to now, bibliometric research has concerned itself primarily with the calculation of percentiles. This study suggests how percentiles can be analysed meaningfully for an evaluation study. Publication sets from four universities are compared with each other to provide sample data. These suggestions take into account on the one hand the distribution of percentiles over the publications in the sets (here: universities) and on the other hand concentrate on the range of publications with the highest citation impact - that is, the range which is usually of most interest in the evaluation of scientific performance. 
Lutz Bornmann
stat.AP cs.DL physics.soc-ph