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Consider a coherent system consisting of independent or dependent components and assume that the components are randomly chosen from two different batches, where the components lifetimes of the first batch are larger than those of the second in some stochastic order sense. In this paper, using different stochastic orders, we compare the reliability of such systems and show that the reliability of the systems increases, as the random number of components chosen from the first batch increases in different stochastics orders.  We use copula function to describe dependence structure between component lifetimes.

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In this article, the number of failures of a coherent system has been studied under the assumption that the lifetime of system components are non-distributed discrete and dependent random variables. First, the probability that exactly

i

Failure
i=0, ..., n-k,

in a system

$k$

From

n

Under the condition that the system at the time of monitoring

t

it works

it will be counted. In the following, this result has been generalized to other coherent systems. In addition, it has been shown that in the case of independence and co-distribution of component lifetimes, the probability obtained is consistent with the corresponding probability in the continuous state obtained in the existing literature. Finally, by presenting practical examples, the behavior of this probability has been investigated in the case that the system components have interchangeable and necessarily non-distributed lifetimes

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This paper explore some extropy properties of the lifetime of coherent systems with the assumption that the lifetime distribution of system components are independent and identically distributed. The presented results are obtained using the concept of system signature. To this aim, we first provide an expression for extropy of the lifetime of coherent systems. Then, stochastic extropy comparisons are discussed for coherent systems under the condition that both systems have the same characteristic structure. In cases where the number of system components is large or the system has a complex structure, it is difficult or time-consuming to obtain the exact extropy value of the system lifetime. Therefore, bounds are also obtained for extropy. In addition, a new criterion for selecting a preferred system based on relative extropy is proposed, which considers the lifetime of the desired system closest to the parallel system.