How do we assure that our customers receive the highest possible quality in our products? The first thing that comes to many people’s minds is that we need to have plenty of inspection. Defective products will get made and we need to catch them before they get to the customer.
Unfortunately, inspection (as well as various kinds of testing) does not catch every defect. No inspection process catches every defect. Many let 20%, 30% and more escape. Inspections can also catch products that turn out not to be defective.
In workshops, we demonstrate the unreliability of inspection by having each participant independently count the number of a certain letter (for example, “e”) that can be found in a text. All counters do not come up with the same number. If the letter were a defect, some would not be caught in the inspection process.
Inspection does not add value. It only catches some of the defective products and leads us to other work that does not add value either, but does add cost.