Which of the following equation is/are not correct? Consider MWT – Mean Waiting time; ADT – Administrative delay time; LDT – Logistic delay time; MDT – Mean down time; MTTR – Mean time to repair; MTTF – Mean time to failure.

Correct Answer: MDT = MTTF + MWT
The equation MDT = MTTF + MWT is wrong because MTTR and MTTF are different. MDT is the total time required to restore a system to a given level performance. Hence, MDT consists of MTTR, ADT and LDT.