Classification assessment criteria

The correct classification rate (CCR) or misclassification rate (MCR) are perhaps the most favoured assessment criteria in discriminant analysis. Their widespread popularity is obviously due to their ease in interpretation and implementation. Other assessment criteria are based on probability measures. Unlike correct classification rates which provide a discrete measure of assignment accuracy, probability based criteria provide a more continuous measure and reflect the degree of certainty with which assignments have been made. In this chapter we present results in terms of correct classification rates, for their ease in interpretation, but use a probability based criterion function in the construction of the filter coefficients (see Section 2.3). Whilst we speak of correct classification rates, misclassification rates (MCR == 1 - CCR) would equally suffice. The correct classification rate is typically formulated as the ratio of correctly classified objects with the total 

Here 8 is an indicator variable such that 5(yi,yj) = 1 if yj = yj and zero otherwise. (For an interesting documentation involving error-rate estimation procedures to simulated data, the reader is referred to [2]). Eq. (6) is based on the training data, and as mentioned earlier, this result is likely to give an overly optimistic impression of the classification model. The correct classification rate for the testing data which is defined by 

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The third criterion is that the model should target an endpoint relevant for REACH. Only models that address the endpoints of interest for REACH are appropriate within this purpose. We notice that REACH mentions different purposes for the QSAR models classification and labeling, is one possible target of the model, and risk assessment in another. In the first case models are classifiers in the second case a regression more is more suitable. Indeed, in the first case the... 

Three criteria are useful when assessing topic relationships, namely (a) the molecular environment, (b) symmetry considerations, and (c) the substitution criterion. When two topic groups in a molecule have stereoisomeric environments, the molecule is said to possess elements of prostereoisomerism. Mislow and Raban have given a definitive classification of topic relationships [62], and the following discussion is based on this classification. 

When the comparative assessment of cumulation of various substances is required, values of their obtained from 0.05 LD,o and 0.1 LDjg administrations are compared. Depending on value, 4 degrees of cumulation can be specified. This criterion was used for the hygienic classification of pesticides. 

A 2011 study by Lithner et al. (2011) assessed the environmental and health hazards posed by plastics, based on the toxicity of their monomers. The classification is not inherent to the polymer as it is based primarily on residual monomer (with selected additives, plasticizer, and flame retardants). The ranking (see Table 8.8) can have relevance only for occupational exposures and in some food-contact uses of plastics. Also, future advances in residual monomer reduction technology and green substitution of additives can change the status of a polymer in this assessment. Where recyclabihty" is used as a ranking criterion, it generally refers to technical recyclabihty that has little to do with if the resin will in fact be recycled in practice. 

Step 2 The safety classification of structures, systems and components reflects the internal postulated events and external events as set forth in the safety analysis of the plant (box (3) of Fig. 1). The definition of the defence in depth levels and barriers [2], the application of the single failure criterion and the assessment of the potential for common cause failures are identified in box (2) of Fig. 1 [19], bearing in mind the categorization of the facility. Next is the evaluation of the need for emergency procedures, both on and off the site. This is followed by identification of the internal events to be considered as a consequence of an external event or as contemporaneous to an external event, and therefore of the safety functions to be maintained in case of an external event (e.g. cooling of radioactive material, reactivity control, confinement). 

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