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100% Inspection

A 100% inspection is exactly what it sounds like. It is a check on every single piece of work. The inspection can be done on both physical products on the shop floor, or information in an office setting.

Most complete inspections such as this come from a few main sources:

  • Government regulations. Some agencies require 100% inspections.
  • Products requiring perfections. This is usually safety related or to protect the perception of the product as high-grade.
  • Demanding customers. Some customers have enough clout to drive action by a company. This may be explicit (the customer demands a 100% inspection), or may be initiated by the company to preserve the relationship in the face of quality problems.
  • Known quality issues. In this case, the extensive inspection is an admission that there are quality problems that the leadership team is unable to address.

The primary purpose of a 100% inspection is to avoid shipping any bad products. The alternative to a 100 percent inspection is a sampling plan, in which the inspection gives an indication of an overall quality level. In a sampling plan, the results of the sample are used to make decisions about what to do with entire product runs rather than to act as a safety net to capture problems.

While a full inspection does find more issues than a sampling plan, there are some problems. The first is that a 100% inspection is generally an indicator that quality is poor. If it is left in place permanently, it also suggests that the company is not focused heavily on continuous improvement, as presumably, an issue that warrants the resources of a 100% inspection should also warrant some problem solving resources. The resources a 100% inspection consumes is the second problem. Complete inspections tend to be very wasteful.

The final problem is that full inspections generate overconfidence. When people operate with a safety net, they may not worry as much about quality, as they know the product will be getting a final look. 100% inspections can undermine quality in a company, rather than build it up.

Be careful about errors in the inspection process. An inspection is not infallible. Every product can obviously be good or bad, and every inspection can result in a pass or fail. Taken together, this gives four possible combinations, two of which represent incorrect outcomes.

  • Good Product Passes: This is the desired outcome.
  • Bad Product Fails: While not desired, this is an outcome that is correct.
  • Good Product Fails: Known as a false positive or a type-I error, the test flags a product it shouldn’t. This costs money, as good products are scrapped. Think of this as crying wolf, albeit unintentionally.
  • Bad Product Passes: In production environments, this is the worse of the two failure types. A false negative, or type-II error, means the test fails to catch a problem.

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