“…An activation/correction model for related design faults is needed. The one proposed is a generalization of the Goel and Okumoto model [4], and is described by the following hypotheses: 1) initially there are k related design faults with probability q k , k ≥ 1, 2) the total related design fault activation rate when k ≥ 1 faults are present is ψ k , 3) a related design fault, when activated, causes identical errors with probability c (error correlation), 4) an activated related desing fault causing a disagreement is diagnosed as such with probability E d (diagnosis efficiency) and with probability 1 − E d is treated as a transient physical fault 1 , i.e., the system is restarted without correction, 5) a diagnosed related design fault is properly corrected in a version with probability E c (correction efficiency), 6) a related design fault not properly corrected in any version leaves the same related design fault activation rate as the system had before.…”