In this research we concern with the comparison between the two ways of
providing redundant units for a system:-
1. Component redundancy.
2. System redundancy.
The comparison between these ways is carried out by comparing the random
variable representing the lifetime of the system resulted from applying component
redundancy with the random variable representing the lifetime of that resulted from
applying system redundancy using some types of stochastic orderings, namely:
(1) usual stochastic ordering, (2) failure rate ordering, (3) likelihood ratio ordering,
(4) reversed failure rate ordering and (5) mean residual life ordering.