Statistics from Altmetric.com
Competing interests None.
Ethics approval The protocol, patient information leaflet and questionnaire were reviewed by Dr Phillip Sedgwick, Reader in Statistics and course organiser at St George's, University of London.
Provenance and peer review Not commissioned; internally peer reviewed.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.