Shewart Papers

Dr Walter A Shewhart, the Father of Quality and Improvement

In 1924, whilst working at Western Electric, Shewhart made the first of two fundamental realisations that have become the foundation stones of quality related to manufactured goods, and improvement in both the quality of manufactured goods and service delivery.

His first breakthrough related to the existence of variation in manufactured products and, specifically, that there were two types of variation, namely Common Cause and Assignable Cause.  Moreover, he produced statistical proofs that treating some outcome measurements as though they were signals for action when in fact they were noise, or treating other outcome measurements as if they came from system noise when in practice they were a signal for action, would lead to greater waste.  He went on to develop the statistical basis for analysis and differentiation of the two causes of variation.  He also proposed acceptable economic statistical limits for distinguishing between the two forms of variation.

In 1939, Shewhart introduced a second key element of scientific method applicable to both manufactured goods and service delivery: hypothesis testing.  He introduced a three-step improvement process based on specification, production and inspection, which is tied into scientific method.  For specification read hypothesis, for production read experiment, and for inspection read test of hypothesis.  Shewhart later realised that these steps needed to go in a circle.

During this period, two other notable figures in the quality and management field, namely J. Juran and W. Edwards Deming, were also working at the Hawthorne Works of Western Electric.  As we know, Deming went on to apply and develop Shewhart’s improvement methods, notably with the Japanese.  Right up to the present day, Shewhart’s contributions continue to influence the daily work of quality, namely in control charts and the Plan-Do-Study-Act (or PDSA) cycle.

In June 1980, Deming wrote in a preface to a reprint of Economic Control of Quality of Manufactured Product by Shewhart; “These problems cannot be understood and cannot even be stated, nor can the effect of any alleged solution be evaluated, without the aid of statistical theory and methods.”   Surely this was an acknowledgement that Deming had understood Shewhart’s fundamental and far-reaching realisation, that statistics are at the heart of quality and improvement.

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