21. Consider the following four structures:

Let F1, F2, and F3 be the corresponding component failure distributions; each of which is assumed to be IFR (increasing failure rate). Let F be the system failure distribution. All components are independent.

(a) For which structures is F necessarily IFR if F1 = F2 = F3? Give reasons.

(b) For which structures is F necessarily IFR if F2 = F3? Give reasons.

(c) For which structures is F necessarily IFR if F1 = F2 = F3? Give reasons.

Transcribed Image Text:

(i) Figure 9.23 2 3 2 3 Figure 9.25 (ii) (iv) Figure 9.24 1 2 3 2 3 Figure 9.26 2 3