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Process evaluations for cluster-randomised trials of complex interventions: a proposed framework for design and reporting

Aileen Grant1*, Shaun Treweek1, Tobias Dreischulte2, Robbie Foy3 and Bruce Guthrie1

Author Affiliations

1 Quality, Safety and Informatics Research Group, Population Health Sciences, Medical Research Institute, University of Dundee, Mackenzie Building, DD2 4BF, Dundee, UK

2 Medicines Management Unit, NHS Tayside, c/o University of Dundee, Mackenzie Building, DD2 4BF, Dundee, UK

3 Leeds Institute of Health Sciences, Charles Thackrah Building, University of Leeds, 101 Clarendon Road, LS2 9LJ, Leeds, UK

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Trials 2013, 14:15  doi:10.1186/1745-6215-14-15

Published: 12 January 2013



Process evaluations are recommended to open the ‘black box’ of complex interventions evaluated in trials, but there is limited guidance to help researchers design process evaluations. Much current literature on process evaluations of complex interventions focuses on qualitative methods, with less attention paid to quantitative methods. This discrepancy led us to develop our own framework for designing process evaluations of cluster-randomised controlled trials.


We reviewed recent theoretical and methodological literature and selected published process evaluations; these publications identified a need for structure to help design process evaluations. We drew upon this literature to develop a framework through iterative exchanges, and tested this against published evaluations.


The developed framework presents a range of candidate approaches to understanding trial delivery, intervention implementation and the responses of targeted participants. We believe this framework will be useful to others designing process evaluations of complex intervention trials. We also propose key information that process evaluations could report to facilitate their identification and enhance their usefulness.


There is no single best way to design and carry out a process evaluation. Researchers will be faced with choices about what questions to focus on and which methods to use. The most appropriate design depends on the purpose of the process evaluation; the framework aims to help researchers make explicit their choices of research questions and methods.

Trial registration NCT01425502

Process evaluation; Complex intervention; Cluster-randomised controlled trial; Qualitative; Quantitative; Reporting