Non-parametric measurement for patient-reported outcomes

We issued the call for the set of papers published in this special section in 2019 with the goal to illuminate innovative state-of-the-art methods for nonparametric measurement. The original idea for this call goes back to a series of potential topics for methodological special sections in our journal collated by our previous Co-Editor in Chief, Frans J. Oort, which we discussed and developed further in our editorial meetings at the International Society for Quality of Life Research (ISOQOL) Annual Conferences in Philadelphia (2017) and Dublin (2018). And I am very grateful to our two excellent guest editors, Klaas Sijtsma and Andries van der Ark, who helped us to finalize the call and who facilitated the project. We received 13 expressions of interest and six full papers were submitted, of which five are published in this special section. …