Another way to lower the cost of quality assurance is to use variable inspections. Because quality levels vary over time, it is only common sense to vary how often we inspect. For instance, if for weeks we don’t find problems, it would seem logical to check less often. But if problems begin to develop, we can test ever more frequently until quality again returns to the previous high levels. The advantage here is still lower costs and even less interference with the production flow. Yet this approach is not used very often, even in widget manufacturing. Why not? Probably because we are
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