The use of multimethodology in operational research practice supporting strategic decision-making: prevalence, methods, designs, and causal mechanisms

Recently, there has been renewed and significant interest amongst both operational research (OR) academics and practitioners in how qualitative analysis methods (such as problem structuring methods) can be used with quantitative analysis methods (such as optimization and simulation) to address complex, strategic issues with stakeholders. However, multimethodology - a term commonly used in OR and systems thinking to describe the use of multiple methods or methodologies within the same project or intervention - is a critical aspect of OR where there is a persistent gap between OR literature and OR practice in non-academic settings. While OR is widely used to tackle important problems in UK government, and it is claimed that UK government practitioners commonly combine qualitative and quantitative OR analysis methods, this is an area of practice where we have few published examples. Further, OR literature sets out a range of influences on practitioner method choice and several reasons (benefits and rationales) for using multimethodology, as well as barriers and challenges. However, there is a lack of empirical evidence of the process by which practitioners choose and combine methods, including the extent to which they use the many theoretical frameworks and typologies for multimethodology found in OR literature. In this dissertation, I present a new review of the prevalence of use of qualitative with quantitative OR, report a new set of six multimethodological designs (forms of multimethodology) that may be more widely applicable across OR practice and mixed methods research, and enhance understanding of the use of multimethodology in OR practice by investigating over 100 decision support interventions supporting strategic decision-making for or on behalf of the UK government. I present and analyse, using descriptive statistics and thematic analysis, 104 cases of multimethod intervention from a survey of 54 practitioners conducted for understanding the research context. I then present a multiple case study, with in-depth, comparative study of five interventions using a multimethod approach that includes insights from project documents and 50 interviews with practitioners and their clients and collaborators. Overall, this applied research provides understanding of theoretical frameworks and terminology for multimethodology, and empirical evidence from this research context of the prevalence of multimethodology, methods used and not used, how, and why, all of which can be employed to ground scholarship on multimethodology, and to support and inform future OR practice, training, apprenticeships, and education. The research adds unique, empirical insights to the growing body of evidence that multimethod practice is commonplace in non-academic settings, and necessary for addressing complex, real-world issues. Moreover, for the multiple case study, and for the first time as far as I am aware, I operationalize critical realism for evaluating the practice of multimethodology in OR. I develop a new, theory-informed, critical realist analysis of a generic multimethodological OR intervention, synthesizing existing empirical research and theories in OR and recent developments in philosophy and social science. I employ the theoretical framework in aiming towards a more theory-informed, causal understanding of why OR practitioners use the methods and methodological designs they do, explaining the context and complex process of practitioners' methodological decisions using rich description, and structural and causal analysis. This new theoretical and methodological approach for evaluating multimethodological practice, developed and employed through the dissertation, can be extended in future in OR to investigate causal mechanisms leading to other individual and collective actions, and intervention outcomes including intervention success. It can also be used across other disciplines to theorize research design and evaluate mixed methods research projects, including their complexity and practical utility.