Cease Mass Inspection for Quality

Comment in response to, Re-Discovering W. Edwards Deming, a partial quote from that post:

Not all of the Deming approach is part of core TPS thinking. In particular, Deming advocated a statistical sampling approach to quality inspection, while Toyota focuses on 100% inspection or eliminating the need for inspection through via the concepts of Poka Yoke and Jidoka. As much as I admire Deming and his philosophy, I agree with the Toyota innovation that it is better to prevent defects from occurring, or at least preventing defects from reaching the customer.

Thanks for your continually interesting blog. I think some might read this post and be confused about what Deming thought about sampling and inspection.

Deming’s point 3 is “Cease dependence on inspection to achieve quality. Eliminate the need for inspection on a mass basis by building quality into the product in the first place.” (Out of the Crisis, 1982). I think Toyota’s improvement of the system to build quality into the product is exactly what Deming had it mind.

Deming believed in improving the process, and doing so using process measures (which often may involve sampling) to guide improvement efforts. He did not believe in using inspection to select out the bad products, which is what inspection largely was before Deming.

He also talked about inspection of incoming material from suppliers – see Chapter 15 of Out of the Crisis.

He also did a great deal of work with sampling to improve population estimates for the US Census Bureau and others as well as on surveys and the sampling involved in surveys.

More on Deming’s thought on Inspection.

[Added to this post, new link: Inspection is too late. The quality, good or bad, is already in the product.]