Inspection does not improve the quality, nor guarantee quality. Inspection is too late. The quality, good or bad, is already in the product. As Harold F. Dodge said, “You can not inspect quality into a product.”
Out of the Crisis, page 29
Inspection can be useful to gather data on the process. Using that data to see if a process has gone out of control and a special cause needs to be investigated is useful. Using that data to evaluate the success, or failure, of an attempt to improve (via the PDSA cycle) is useful.
Inspecting to pull out the failed items from the production before a customer sees them is a path to failure. If the process is this bad, the process needs to be improved. If you can actually stay in business doing this now, you are at risk for not being able to stay in business when the market stops being willing to pay you to produce results people don’t want.
I am reminded of how impressed with Dr. Deming’s crediting others. A number of the quotes people credit to Dr. Deming he notes the proper author in his book. I understand that people learn to associate these quotes with Dr. Deming, but I still find it amusing. It also shows his devotion to learning and desire for accurate documentation.
“Quality can not be inspected into a product or service; it must be built into it.” – Out of the Crisis page 227 (where Dr. Deming again refers readers to Dodge’s quote that Dr. Deming included earlier in the book)