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Resistors can be purchased with known quality and failure rate levels. These are determined by the resistor vendor through testing. Resistors manufactured to the Military performance specifications are identified by a failure rate letter designator, shown in Table 1.  The failure rates of Military standard resistors carry a statistical confidence level of 60% based on life test at full rated power and temperature, usually with a 10% producer’s risk.  Commercial resistors can also be purchased with given quality/failure rating, although testing methods and statistical confidence levels will vary between part vendors.

Quality assurance requirements imposed on the resistor vendor depend on the quality level of the resistor. Resistors conforming to the Established Reliability (ER) requirements of Military performance requirements are required to undergo Group A, B, and C testing on a periodic basis. A comparison of some of the more common conformance tests for the MIL-PRF standards is given in Table 2 for Group A testing, Table 3 for Group B, and Table 4 for Group C. As the tables show, tests are different for different resistor styles. Note these are not comprehensive tables of all Group A, B, and C tests. In addition, the procedures covering the detailed implementation of the tests may differ between specifications. For more detailed information, consult the data sheet, resistor manufacturer, and military performance specification. Military performance and specification requirements are given under the "Military Considerations" paragraph for each resistor style (Resistor Derating section). Some resistor styles have no governing Military performance specifications, and therefore the Military considerations are marked as not applicable.

Table 2. Sample of Group A Inspection-Test Requirements for Resistors

Table 3. Sample of Group B Inspection-Test Requirements for Resistors

Table 4. Sample of Group C Inspection-Test Requirements for Resistors