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A Risk is the amount of harm that can be expected to occur during a given time period due to specific harm event (e.g., an accident). Statistically, the level of risk can be calculated as the product of the probability that harm occurs (e.g., that an accident happens) multiplied by the severity of that harm (i.e., the average amount of harm or more conservatively the maximum credible amount of harm). In practice, the amount of risk is usually categorized into a small number of levels because neither the probability nor harm severity can typically be estimated with accuracy and precision. A Risk Matrix is a matrix that is used during Risk Assessment to define the various levels of risk as the product of the harm probability categories and harm severity categories. This is a simple mechanism to increase visibility of risks and assist management decision making. Although many standard risk matrices exist in different contexts (US DoD, NASA, ISO),〔United States Department of Defense, Risk Management Guide for DoD Acquisition, August 2006〕〔Goddard Space Flight Center, NASA, Risk Management Reporting, GSFC-STD-0002, 8 May 2009〕〔International Organization for Standardization, Space Systems Risk Management, ISO 17666,〕 individual projects and organizations may need to create their own or tailor an existing risk matrix. For example, the harm severity can be categorized as: *Catastrophic - Multiple Deaths *Critical - One Death or Multiple Severe Injuries *Marginal - One Severe Injury or Multiple Minor Injuries *Negligible - One Minor Injury The probability of harm occurring might be categorized as 'Certain', 'Likely', 'Possible', 'Unlikely' and 'Rare'. However it must be considered that very low probabilities may not be very reliable. The resulting Risk Matrix could be : The company or organization then would calculate what levels of Risk they can take with different events. This would be done by weighing up the risk of an event occurring against the cost to implement safety and the benefit gained from it. ==An Example== The following is an example risk matrix with certain accidents allocated to appropriate cells within the matrix: 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「risk matrix」の詳細全文を読む スポンサード リンク
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