Qualitative Approach to Criticality

Additional Resources > Windchill Risk and Reliability Practitioner’s Guide > Failure Mode and Effects Analysis > Criticality Analysis > Qualitative Approach to Criticality

According to Task 102 in MIL-STD-1629, the availability of specific parts configuration data and failure rate data determine whether a qualitative or quantitative approach to criticality is to be used. The qualitative approach groups individual failure mode probabilities of occurrence into distinct, logically defined groups that establish the criticality value to be entered in the appropriate column of the FMEA worksheet. Table 6-5 defines the criticality groups for Task 102 when a qualitative approach is used.

Table 6-5. Qualitative Approach to Criticality Analysis (Continued)
Criticality Group	Probability Criteria
Level A - Frequent	Single failure mode probability is greater than 0.20 of the overall probability of failure during the item operating time interval.
Level B - Reasonably Probable	Single failure mode probability is greater than 0.10 but less than 0.20 of the overall probability of failure during the item operating time.
Level C - Occasional	Single failure mode probability is greater than 0.01 but less than 0.10 of the overall probably of failure during the item operating time.
Level D - Remote	Single failure mode probability is greater than 0.001 but less than 0.01 of the overall probability of failure during the item operating time.
Level E - Extremely Unlikely	Single failure mode probability is less than 0.001 of the overall probability of failure (essentially zero) during the item operating time.