Footnotes

• Twitter @dataextips

• Correction notice This article has been corrected since it appeared Online First. A Disclaimer endnote has been added.

• Contributors KST and KRM conceived the idea of the series of which this is one part. KST wrote the first draft of the manuscript. All authors revised the manuscript and agreed the final version.

• Funding This research was supported by the National Institute for Health Research Applied Research Collaboration Oxford and Thames Valley at Oxford Health NHS Foundation Trust.

• Disclaimer The views expressed in this publication are those of the authors and not necessarily those of the National Institute for Health Research or the Department of Health and Social Care.

• Competing interests KRM and JA were Associate Editors of BMJ Evidence Medicine at the time of submission.

• Patient consent for publication Not required.

• Provenance and peer review Commissioned; internally peer reviewed.