1. The following diagram is a fault tree analysis (FTA) of a system that consists of 3 assemblies.

If the system fails, history has shown that each assembly has a certain probability of being the

cause of the failure. Further, history has shown that, within each assembly, the failure could

be component or workmanship. Component failures could be caused by memory, logic or

passive components. Workmanship failures could be caused by opens (open circuit) or shorts

(short circuits). The probability of each type of failure for each level is shown in the diagram.

System fails

Component

2016

Memory Logic

CO%

Passive

Assembly 1 fails

30%

Workmanship

80%

Opens Shorts

40%

DON

Assembly 2 fails

Component

Memory Logic Passive

CO%

Workmanship

Opens Shorts

40% 00%

Assembly 3 fails

30%

Component

20%

Memory Logic Passive

DON 10%

Workmanship

BON

Opens Shorts

40% DON

If the system fails, what bottom level (in the tree structure) type of failure is the

most likely cause, and in which assembly does it most likely reside?

If the system fails, what is the probability that the failure is being caused by a

memory component?