Probability assessment defined

Should any assessment endpoints be expressed as probabilities Suter (1998) points out that it can be confusing to use the term probability in defining assessment endpoints because it is unclear whether it relates to variability or uncertainty, so it will be helpful to distinguish these in the discussion with the risk manager. 

These probabilities are combined appropriately for each event tree sequence, providing a basis for an overall probability assessment for each sequence, and an assignment to a frequency bin defined in the SAR. This is accomplished in the following probability table. Table 3E.2-1. 

The next step requires a probability assessment be conducted for the hazard. The probability that an injury or illness will result from a hazard has no role in determining the classification of a violation, but does affect the amount of the penalty. The probability is categorized either as greater or as lesser probability, defined as follows ... 

When performing a probabilistic performance assessment, data on the acceptable probabilities of the exceedance of a given limit state are needed. There are different approaches to define acceptable probabilities of exceedance of a given limit state (Melchers 1999). However, in the earthquake engineering community there are no generally accepted values for acceptable probabilities of exceedance of a given limit state. In the example, the acceptable probability was defined as follows the probability of exceedance of the NC limit state should not exceed 2% in 50 years (0.0004) with the 90% confidence level. Basically the same definition was used by Yun et al. (2002). 

Although not mandatory in the HAZOP method, this study comprised a risk assessment to all deviations detected. Risk assessment was performed through the use of a risk matrix already used in similar industries which included the combination of probability (possibility that the event occurs) and severity (as a consequence of the event). For the risk assessment criteria, four levels of probability were defined very unlikely/remote, likely/possible, probable and frequent. For severity were defined also four levels reduced, moderate, high, very high/catastrophic. The designation of risk parameters took into account the probability of occurrence, the measures implemented, historical events, potential injury to persons, to materials, to the environment. The combination between the four levels lead to four types of risk, grouped in two levels, acceptable/not significant, which even... 

Step 3 Having the sublanguage defined for each state of the considered system we can obtain firstly the probabihty for a sublanguage and secondly the probabilities for events sequences belonging to this sublanguage. To illustrate the sequence probabilities assessment, the results obtained for two sublanguages (Lj and L ) are presented in this paper. 

In order to assess the criticality of a security attack, severity and probability of the attack needs to be evaluated. While the severity can be assessed with the help of domain experts, probability is defined differently for safety and security. 

Since 1970 tlie field of healtli risk assessment Itas received widespread attention witliin both tlie scientific and regulatoiy committees. It has also attracted tlie attention of the public. Properly conducted risk assessments have received fairly broad acceptance, in part because they put into perspective the terms to. ic, Itazard, and risk. Toxicity is an inlierent property of all substances. It states tliat all chemical and physical agents can produce adverse healtli effects at some dose or under specific exposure conditions. In contrast, exposure to a chemical tliat lias tlie capacity to produce a particular type of adverse effect, represents a health hazard. Risk, however, is tlie probability or likelihood tliat an adverse outcome will occur in a person or a group tliat is exposed to a particular concentration or dose of the hazardous agent. Tlierefore, risk can be generally a function of exposure and dose. Consequently, healtli risk assessment is defined as tlie process or procedure used to estimate tlie likelihood that... 

Following a theoretical analysis of distributed small-plant manufacture, Benson and Ponton define assessment criteria for processes suitable for such processing [139]. Since micro reactors are one of the favorite and natural tools for distributed manufacture, this selection list also defines micro-reactor applications. In this context, the authors, probably in one of the first regular citations, emphasize that formulation processes, especially those with multiple ingredients, are particularly suited for distribution. The making of paint on-site is referred to as an already existing way to do so. It stands to reason to augment the scope from formulations to functional chemicals. 

Because the goal of hit triage is to identify chemical series that hold promise for further optimization, an approach to characterize the ADME properties of a series, not just individual compounds is often useful. Where possible, characterizing the structure-ADME property relationship, in much the same way that a structure-potency relationship is defined, can be valuable for assessing the probability that a given structural series can be successfully optimized. The goals of this ADME property characterization are twofold (1) to identify specific structural features that may be liabilities (benefits), and (2) to identify general structure-ADME property correlations. 

The organization for economic co-operation and development (OECD) defines risk assessment as the process intended to calculate or estimate the probability, including the identification of attendant uncertainties, of an adverse effect in an... 

Assessment of the geographical distribution of pollution in the river using fish samples is more difficult than in the case of SEs, probably because of their mobility, which in some cases can lead to confusing results. PCI identified in fish samples defines a contrast between two inversely correlated contamination profiles. Positive... 

Let us use some of the methods applied to the germanium compounds to assess a few values from Table 3. A plot of the three gaseous enthalpies of formation for tetraethyl, tetra-n-propyl and tetra-n-butyl tin species versus the number of carbon atoms in the compound (equation 1) shows that probably at least one of them is inaccurate. In the liquid phase there is an additional enthalpy of formation, that for tetra-w-hexyl tin. A plot of the liquid enthalpies of formation versus total carbon number shows that the enthalpy of formation for tetraethyl tin is an outlier and the remaining three points define a fairly good straight line15 (r2 = 0.99953, a = -21.77 0.80, = 47.78 12.39). If... 

The authors also evaluated the performance of various DES-T and DES cutoffs for detecting taxon members defined by Bayesian probabilities. Waller and Ross found that DES-T cutoffs work much better than the cutoffs on the DES because they have higher sensitivity, specificity, and positive and negative predictive values. One could say that the authors stacked the deck in favor of the DES-T, as the Bayesian probabilities and DES-T scores are based on the same data. However, this redundancy is unavoidable, since there is no other method of assessing taxon membership. It is important to evaluate the qualities of DES-T cutoffs for studies that will use the DES-T, rather than the Bayesian scoring scheme. 

In use of risk assessment methods, you will find that the methodology for calculating overall risk probabilities is quite well defined. But, assigning realistic values to individual probabilities can be quite difficult, and a matter of personal opinion of the analyst. So, the analyst must have intimate knowledge of the system being evaluated, as well as all effects being considered, before he can make an acceptable risk assessment. 

Hazard is commonly defined as the potential to cause harm . A hazard can be defined as aproperty or situation that in particular circumstances could lead to harm (Smith et al., 1988). Risk is a more difficult concept to define. The term risk is used in everyday language to mean chance of disaster . When used in the process of risk assessment it has specific definitions, the most commonly accepted being The combination of the probability, or frequency, of occurrence of a defined hazard and the magnitude of the consequences of the occurrence (Smith et al., 1988). 

In accordance with this definition, an environmental risk assessment process is used especially in cases when the probability component arises during the calculation of various parameters which can be due to many reasons uncertainty of input information uncertainties in applying an algorithm due to lack of knowledge, insufficient knowledge and/or simplification of input information uncertainties in the defined geographic boundaries of pollutant influence uncertainties in both computer calculations and management operations based on these calculations. 

Crawley and Grant (1997) have developed a risk assessment tool for new offshore installations. They have examined typical leak frequencies of equipment items and the ignition probability of these leaks in four pressure bands. With this information it was possible to define leak size and frequency for any piece of equipment and the ignited leak frequency. In off-shore installations gas separation vessels were found to have ten times higher ignited event frequency than oil pumps. 

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