This paper demonstrates an approach to include conditional probabilities when calculating probabilities of disaster in quantitative risk analysis. Since not all layers of protection are independent of each other, using conditional probabilities leads to more accurate calculations of probabilities of disaster in a chemical process. An event tree analysis approach is shown by calculating probabilities of disaster assuming that events are statistically independent (independence assumption), and separately considering that events affect each other (conditional probabilities), in three cases with increasing complexity and number of layers of protection. For each case, we considered multiple scenarios to show that results do not depend on the input probabilities of particular events. In most scenarios of the three cases, findings demonstrate that the probabilities of disaster calculated using the independence assumption are lower than those with conditional probabilities, which can lead to undercounting the layers of protection that are actually needed.

中文翻译：

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比较保护分析各层中的条件概率和统计独立性

本文演示了一种在定量风险分析中计算灾难概率时将条件概率包括在内的方法。由于并非所有的保护层都彼此独立，因此使用条件概率可以更准确地计算化学过程中的灾难概率。在三种情况下，随着复杂性和保护层数的增加，假设事件在统计上是独立的（独立假设），并考虑事件相互影响（条件概率），则通过计算灾难概率来显示事件树分析方法。对于每种情况，我们考虑了多种情况，以表明结果不取决于特定事件的输入概率。在这三种情况的大多数情况下，