Qualitative vs quantitative modelling: The evolving balance

This paper addresses the issue of what are the wise uses of qualitative mapping and what are the conditions that require formal quantitative modelling within System Dynamics. The background to the evolution of qualitative and quantitative system dynamics is explored. This analysis recognises that, although the history of feedback thought repeatedly contains the assertion that formal, quantitative models are essential for understanding the dynamics of complex systems, the need for quantification is relative and depends on the purpose of analysis, which, in turn, is related to the methods used and the audience addressed. The central theme of the paper is to examine the strengths and weaknesses of qualitative and quantitative system dynamics and to relate these to their respective tool sets. The paper also focuses on evidence from the author's extensive recent use of qualitative and quantitative system dynamics in education, training, research and consultancy studies of the way in which qualitative and quantitative system dynamics can be linked together to consolidate management learning, both in projects and in organisations. The paper concludes that both qualitative and quantitative system dynamics are important to management problem solving and related to the purpose of analysis. It is suggested that within studies the true power of system dynamics to address problem solving lies in a judicious blend and intertwining of both qualitative and quantitative ideas, aimed at addressing as broad an audience as possible whilst remaining sufficiently rigorous to be useful. A process referred to as intertwined project learing (IPL) is outlined for this purpose. Within organisations it is suggested that there is a need to link the use of qualitative system dynamics in management development programmes and quantitative system dynamics modelling projects into an integrated organisational learning activity. A process referred to as accelerated business learning (ABL) is outlined for this purpose.