Comparing and ordering of uncertain random variables give a guideline to make decisions in uncertain random environments, so we study the comparison of two uncertain random variables. For this purpose,we define a new order which we call the chance order and study some of its basic properties. We then apply the results to order the lifetime of the k-out-of-n systems when the lifetimes of some components of the system are random variables while the others are uncertain variables. It is worth mentioning that when two uncertain random variables are both random variables or uncertain variables, the chance order becomes the stochastic order and the uncertain dominance, respectively. That is, the concept of chance order of uncertain random variables extends the concepts of the stochastic order of random variables and the uncertain dominance of uncertain variables.

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