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Diagnostic problem solving, which is the task of discovering causal explanations for unwanted effects, is an important element of problem solving. This paper contributes a conceptual framework for the generic process of diagnosis in quality problem solving by identifying its activities and how they are related. It then presents six strategies that structure the diagnostic process by suggesting a certain sequence of actions and techniques. The paper analyzes when each of these strategies is likely to be effective and how it may help in making the diagnostic process more efficient. Finally, the paper proposes and motivates a generic sequence of stages in diagnosing quality problems.
The framework offers a scientific basis for studying and evaluating problem-solving methodologies such as Six Sigma's DMAIC model. Kepner and Tregoe's problem analysis method, and Shainin's system. For the practitioner, the framework clarifies the rationale for many problem-solving techniques offered in courses and textbooks. The paper also offers indications and contra-indications when techniques are promising, and demonstrates how they fit together in a coherent strategy.
Key words: diagnosis, DMAIC, problem solving, rootcause analysis
INTRODUCTION
Problem solving in the face of quality, reliability, and performance problems has been and still is an important task in operations management (for example, Balakrishnan et al. 1995; Ho and Sculli 1997; MacDuffie 1997). In recent years, large numbers of professionals have been trained in advanced problem-solving methodologies, and the Six Sigma phenomenon in particular has spurred a flood of courses and textbooks on problem solving following its define-measure-analyze-improve-control (DMAIC) model (Chakravorty 2009; de Mast and Lokkerbol 2012). The 1980s and 1990s saw the emergence of problem-solving approaches such as the Shainin System (Shainin 1993; Steiner, MacKay and Ramberg 2008) and Kepner and Tregoe's (1997) problem analysis method, still widely taught and applied in industry. Simpler models, such as the plan-do-check-act (PDCA) and eight disciplines (8D) models, are also generally applied, as well as techniques such as root cause analysis, brainstorming, 5 Whys, and the cause-and-effect diagram.
The discovery of the causes of a problem is called diagnosis, and it is an essential element of problem solving. This paper contributes a conceptual framework for the diagnosis process in quality problem solving. It then presents six strategies that structure the diagnostic process using a certain sequence...