To be acceptably safe one must identify the risks one is exposed to and decide what risk reducing measures are required. It is uncertain whether the threat really will materialize, but determining the size and probability of the risk is also full of uncertainty. When performing an analysis and preparing for decision making under uncertainty, quite frequently failure rate data, information on consequence severity or on a probability value, yes, even on the possibility that an event can or cannot occur, is lacking. In those cases, a possible way and sometimes the only way to proceed is to revert to expert judgment. Even in case historical data is available, an expert can be asked whether and to what extent such data still hold in the current situation.

Anyhow, expert elicitation comes with an uncertainty depending on the expert's reliability, which becomes very visible when two or more experts give different answers or even conflicting answers. This is not a new problem, and very bright minds have thought how to tackle this in a rational and objective way. But so far, however, the topic has not been given much attention in daily process safety and risk assessment practice. Therefore, this paper has a review and applied character and will present various approaches with detailed explanation and examples.

为了获得可接受的安全，必须识别一个人所面临的风险并决定需要采取哪些降低风险的措施。不确定威胁是否真的会实现还不确定，但是确定风险的大小和可能性也充满不确定性。当进行分析并为不确定性下的决策做准备时，经常会出现故障率数据，后果严重性或概率值的信息，甚至是缺少事件可能或不可能发生的信息。在这种情况下，一种可行的方法（有时甚至是唯一的方法）是恢复专家的判断。即使有历史数据，也可以询问专家在当前情况下这些数据是否仍然保留以及保留到何种程度。

无论如何，专家启发会带来不确定性，具体取决于专家的可靠性，当两个或多个专家给出不同的答案甚至矛盾的答案时，这种不确定性就变得非常明显。这不是一个新问题，非常聪明的人已经想到了如何以理性和客观的方式解决这个问题。但是，到目前为止，在日常过程安全和风险评估实践中并未对该主题给予太多关注。因此，本文具有回顾性和应用性，并将提供各种方法以及详细的解释和示例。