It is often necessary or advantageous to examine differences between processes (or technologies), for the purpose of making business decisions. Statistical thinking is needed to evaluate the impact of process or other changes on organizational performance. In statistical thinking, past experience is summarized or generalized. Statistical thinking allows us to make predictions and reach conclusions.
In the course of the twentieth century statistical methods have come to play an ever more important role in quality improvement in industry. In this context, statistical methods were made operational in the form of statistical improvement strategies. It is the purpose of this paper to develop a methodological framework for statistical improvement strategies. Such a framework should provide definitions of relevant concepts, methodological rules and heuristics, both to help the practitioner carry out an improvement project and as a paradigm for the researcher.
The link between quality improvement and statistics is formed by empirical inquiry. Namely, quality improvement projects can be regarded as empirical inquiry and it is in this context that statistical methods are applied in quality improvement. In quality improvement, the suggestion to consider statistical method in the context of empirical inquiry was supported by, for example, Box and Liu , who refer to statistics as ‘a catalyst to learning by scientific method’. The function of empirical inquiry is to explain empirical phenomena and, as a consequence, predict and control such phenomena. Explanations of empirical phenomena provide understanding by showing that the phenomenon to be explained should be expected as a consequence of certain causal influence factors.
Predictions have the same structure as explanations: where explanations show that observed phenomena follow from the laws underlying their behavior, predictions show which unobserved phenomena would follow from these laws if conditions changed. Control consists of the application of explanations and predictions for one’s benefit......
