What are prevention, appraisal and failure costs?

We can describe these costs as follows

Prevention cost:
•Quality planning
•Formal technical reviews
•Testing equipment
•Training
Appraisal cost:
•In-process and inter-process inspection
•Equipment calibration and maintenance
•Testing
Failure cost:
•Internal failure cost: rework, repair, and failure mode analysis
•External failure cost: complaint resolution, product return and replacement, help line support, warranty work