Key takeaways
Short answer: Prevention and appraisal are two of the four cost-of-quality categories, and both are money spent on conformance. They work very differently. Prevention spending stops defects at the source, before a unit is ever made. Appraisal spending checks whether the work came out right, after the fact.
Prevention is usually the higher-return of the two. For the costs these categories exist to avoid, see internal vs external failure costs .
Prevention costs are the money you spend to stop defects from occurring in the first place. They are investments that attack quality problems at the source, before any defective unit is made.
Typical prevention spending includes:
The defining feature is timing. Prevention is spent upstream, before production, to make defects less likely. It is the most proactive cost-of-quality category and generally the highest-return: a dollar spent preventing a defect typically saves several dollars that would otherwise go to detecting, reworking, or recovering from it.
Put simply, prevention is spending to make quality happen, not spending to check whether it did. That is why mature quality programs deliberately shift money toward it.
Appraisal costs are the money you spend to detect defects, to find out whether the output actually conforms.
Typical appraisal spending includes:
The defining feature is that appraisal is spent to assess conformance after the work is done, to catch defects before they reach the customer. It is necessary, because you do need to know whether your output is good.
But appraisal is fundamentally detective, not preventive. It finds defects that have already been made; it does not stop them being made. Every defect it catches is a unit that was still produced wrong, consuming capacity. Appraisal verifies quality. It does not create it. The yield it feeds, like first pass yield, only describes the result.
The cleanest way to see the difference is one question: does the spending change the defect rate, or only measure it?
This is why prevention compounds and appraisal does not. Add inspectors and you catch a little more each shift, forever. Fix the root cause once and the defects stop, so the inspection was never needed in the first place.
Suppose a defect escapes to a customer. A rough but widely used rule of thumb, the 1-10-100 rule, frames the cost:
The exact multiples vary by industry, but the shape holds: the earlier you spend, the less you spend in total. A team that pours money into appraisal is paying to find 10-unit problems instead of paying a little to remove them at the 1-unit stage.
Most plants start appraisal-heavy. Inspection is visible and easy to add, so the instinct under pressure is to add another check.
The higher-return move is to convert appraisal findings into prevention. Each recurring defect that inspection keeps catching is a candidate for a permanent fix: a process change, an error-proofing device, a maintenance task. As prevention rises, the defect rate falls, and the appraisal you needed to catch those defects can come down with it.
The signal to watch is the ratio. A program spending heavily on appraisal and little on prevention is paying to live with its defect rate rather than reduce it.
Prevention and appraisal both land in the quality factor of OEE, but from opposite directions.
Effective prevention raises first-pass quality, so fewer good-unit losses ever reach the quality calculation. Appraisal mostly relocates the loss: a defect caught at final inspection is still a quality loss, it just did not reach the customer.
When you trend the quality factor against where you spend, the pattern is clear. Plants that invest in prevention see the quality factor climb and stay there. Plants that lean on appraisal hold the line but never gain.
Knowing prevention beats appraisal is the easy part. The hard part is seeing, in real time, which defects keep recurring and which prevention action would remove them.
Fabrico ties the quality losses in your OEE stream to the assets and work orders behind them, so a recurring defect becomes a prioritized prevention task instead of one more thing the inspector catches. To see how that looks against your own lines, book a demo.
Yes. Both are costs of conformance, the money you spend to achieve quality, as opposed to failure costs, which are the money you lose when quality slips. The goal is not to eliminate them but to shift the mix toward prevention, where the return is higher.
Sometimes. When a new product launches or a process is unstable, more inspection is a sensible short-term safety net. The mistake is leaving it there permanently instead of using what it finds to drive prevention.
Track the split between prevention and appraisal spend, and watch the defect rate beside it. If appraisal is high, prevention is low, and the defect rate is flat, you are paying to detect a problem you are not fixing.
It is a prevention cost. Equipment that drifts out of spec produces defects, so a working preventive maintenance schedule is one of the most direct ways to prevent quality losses at the source.
Both categories act on the quality factor of OEE. Prevention raises first-pass quality so the loss never occurs; appraisal catches the loss after it occurs. Trending the quality factor against your prevention and appraisal spend shows which approach is actually moving the number.
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