Quantifying and addressing uncertainty in the measurement of interdisciplinarity

A common method for quantifying the interdisciplinarity of a publication is to measure the diversity of the publication's cited references based on their disciplines. Here we examine the criteria that must be satisfied to develop a meaningful interdisciplinary measure based on citations and discuss the stages where uncertainty or bias may be introduced. In addition, using the Rao-Stirling diversity measure as an exemplar for such citation-based measures, we show how bootstrapping can be used to estimate a confidence interval for interdisciplinarity. Using an academic publication database, this approach is used to develop and assess a reliability measure for interdisciplinarity that extends current methods. Our results highlight issues with citation analysis for measuring interdisciplinarity and offer an approach to improve the confidence in assessing this concept. Specific guidelines for assessing the confidence in the Rao-Stirling diversity measure and subsequently other similar diversity measures are presented, hopefully reducing the likelihood of drawing false inferences about interdisciplinarity in the future.