Likelihood probabilities

Objective Provide a basis to judge the relative likelihood (probability) and severity of various possible events. Risks can be expressed in qualitative terms (high, medium, low) based on subjective, common-sense evaluations, or in quantitative terms (numerical and statistical calculations). 

Risk analysis is an assessment of tlie likelihood (probability) of an accidental release of a hazardous material and tlie actual consequences that might occur, based on tlie estimated vulnerable zones. The risk analysis is a judgment of probability and severity of consequences based on tlie history of previous incidents, local experience, and tlie best available current technological information. It provides an estimation of ... 

The likelihood (probability) of an accidental release based on tlie history of current conditions and controls at tlie facility, consideration of any unusual environmental conditions (e.g., areas in flood plains), or tlie possibility of simultaneous emergency incidents (e.g., flooding or fire liazards resulting in tlie release of hazardous materials). 

Risk is defined as a measure of human injury, environmental damage, or economic loss in terms of both the incident likelihood (probability) and the magnitude of the loss or injury (consequence) (AICHE/CCPS, Guidelines for Chemical Process Quantitative Risk Analysis, 2d ed., American Institute of Chemical Engineers, New York, 2000, pp. 5-6). It is important that both likelihood and consequence be included in risk. For instance, seat belt use is based on a reduction in the consequences of an accident. However, many people argue against seat belts based on probabilities, which is an incorrect application of the risk concept. 

Usually it is better and more effective to remove the hazard and make the facility more intuitively safe. If there is no practical method to remove the hazard, the likelihood (probability) for reducing the event consequences should be considered next. Finally if the probabilities cannot be reduced the consequences should be evaluated with additional protective measures. 

Risk The combination of the expected likelihood./probability (events/yr.) and... 

Entropy is closely associated with probability. The key concept is that the more ways a particular state can be achieved, the greater is the likelihood (probability) that that state will occur. In other words, nature spontaneously proceeds toward the states that have the highest probabilities of existing. This conclusion is not surprising at all. The difficulty comes in connecting this concept to real-life processes. For example, what does the spontaneous rusting of steel have to do with probability ... 

Risk analysis is an assessment of the likelihood (probability) of an accidental release of a luizardous material and tlie actual consequences tliat might occur, based on tlie estimated vulnerable zones. It provides an estimation of tlie likelihood (probability) of an accidental release, tlie severity of consequences of human injuiy that may occur, the severity of consequences on critical facilities, tlic severity of consequences of damage to property, and the severity of consequences of damage to tlie enviromnent. Risk characterization estimates tlie healtli risk associated with tlie process under investigation. The result of tins cliaracterization is a number tliat represents tlie probability of adverse healtli effects from tliat process or from a substance released in tliat process. Tire major types of risk include Individual Risk, Maximum Individual Risk (MIR), Population Risk (PR), Societal Risk, and Risk Indices. 

The likelihood (probability) would be approximately 0.36 given that each of the ranges are approximately 36% of the total pressure span ... 

The risk equation shows a useful way to think about risk as a combination of the nature (severity) of the hazard and the likelihood (probability) of the hazardous event occurring. 

We do not need to supply all the parameters in an attribute instance in a query. For example, we can write attributes has risk(likelihood(probable)) to mean find a node with an attribute risk whose iikeiihood is probable and with any severity. We can abbreviate this further by writing attributes has risk(probable), which will look for any parameter with value probabie, or even attributes has risk with which to find nodes tagged with any risk values. We can omit the second argument of a top-level quantifier, in which case it is taken to be true. For example, a root node can be queried by not(isBelow), which is equivalent to not(isBelow)frMe. A derived syntax for queries is given as ... 

We have already stated that risk is a combination of accident likelihood (probability) and severity of the consequence. The risk increases with either severity or the probability of the accident as illustrated in Fig. 4.2. Different regulatory authorities use a variety of classification criteria in order to evaluate the acceptability of risk. Some of these are discussed in more detail in Appendix B, but the remainder of this paragraph wiU use the UK MoD criteria to illustrate the basic approach adopted by most. 

Suppose earlier laboratory tests of the soil used in the earth embankment indicated that a density of less than 100 Ib/ft would be highly undesirable and likely to cause subsidence of the structure. The results shown in this example indicate that even though the mean densities are 120 Ib/fh, there is still a small likelihood (probability = 0.0228) that unacceptably low densities (<100 Ib/ft )... 

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