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1·This is a chance variable, and is not convenient to use in practice.

这是一个随机变量，在实际中不便使用。

2·The second Part is about the exPression of Average stutistics. values for stationary chance variable and its terms concerned.

第二部分是有关平稳随机变量均值的函数表达式及其有关术语。

3·The Bell X-5 gave NACA and Air Force researchers a chance to test out variable-sweep wings.

在贝尔x - 5和空军赋予的NACA研究人员一个机会来测试可变后掠翼。