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Aggregate Failure Rate Algorithmn

 
Description
The Aggregate Failure Rate is the cumulative failure rate associated with the given hierarchical design. Representing the number of system failures per million hours, this metric is based on the adjusted failure rates associated with all used functions that fall within the scope of the specified diagnostic study.
 
Calculation
This Test limit is calculated by summing the adjusted failure rates associated with all lowest-level, used functions that fall within the Diagnostic Scope of the diagnostic study:
 
 
where
N
=
the total number of used functions in the hierarchical design
Li
=
1 if the ith function is a lowest-level function; 0 otherwise
Si
=
1 if the ith function is in the selected Diagnostic Scope; 0 otherwise
FRi
=
the adjusted failure rate of the ith function
 
Note: This metric is calculated using data derived during diagnostic processing and therefore properly takes into account any subsets that can only be elaborated by the diagnostic engine (such as Failure Severity-Based Subsets). This differs from the Aggregate Failure Rate (in Scope) report calculation within the Aggregate Reliability Report, which only takes into account subsets that can be fully elaborated prior to running diagnostics.