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CREAM (Cognitive Reliability Error Analysis Method) is a human reliability analysis technique developed by Erik Hollnagel. It is a bi-directional analysis method, meant to be used for both performance prediction and accident analysis. Unlike first generation error analysis methods like THERP, CREAM represents a second generation tool allowing for better analysis by abandoning the hierarchical structure of previous methods and providing better separation between objective and subjective error. CREAM is a technique used in the field of human reliability assessment (HRA), for the purposes of evaluating the probability of a human error occurring throughout the completion of a specific task. From such analyses measures can then be taken to reduce the likelihood of errors occurring within a system and therefore lead to an improvement in the overall levels of safety. There exist three primary reasons for conducting an HRA; error identification, error quantification and error reduction. As there exist a number of techniques used for such purposes, they can be split into one of two classifications; first generation techniques and second generation techniques. First generation techniques work on the basis of the simple dichotomy of ‘fits/doesn’t fit’ in the matching of the error situation in context with related error identification and quantification and second generation techniques are more theory based in their assessment and quantification of errors. HRA techniques have been utilised in a range of industries including healthcare, engineering, nuclear, transportation and business sector; each technique has varying uses within different disciplines. CREAM is a second generation HRA method. However compared to many other such methods, it takes a very different approach to modelling human reliability. There are two versions of the technique, the basic and the extended version, both of which have in common two primary features; ability to identify the importance of human performance in a given context and a helpful cognitive model and associated framework, usable for both prospective and retrospective analysis. Prospective analysis allows likely human errors to be identified while retrospective analysis quantifies errors that have already occurred. The concept of cognition is included in the model through use of four basic ‘control modes’ which identify differing levels of control that an operator has in a given context and the characteristics which highlight the occurrence of distinct conditions. The control modes which may occur are as follows: * Scrambled control: the choice of the forthcoming action is unpredictable or haphazard. The situation in question may be portraying rapid alterations in unexpected ways thus eliminating the operator’s ability or opportunity to make deductions about the next action required. * Opportunistic control: the next action is determined by superficial characteristics of the situation, possibly through habit or similarity matching. The situation is characterised by lack of planning and this may possibly be due to the lack of available time. * Tactical control: performance typically follows planned procedures while some ad hoc deviations are still possible. * Strategic control: plentiful time is available to consider actions to be taken in the light of wider objectives to be fulfilled and within the given context. The particular control mode determines the level of reliability that can be expected in a particular setting and this is in turn determined by the collective characteristics of the relevant Common Performance Conditions (CPCs). ==Background== CREAM was developed by Eric Hollnagel in 1998 following an analysis of the methods for HRA already in place. It is the most widely utilised second generation HRA technique and is based on 3 primary areas of work; task analysis, opportunities for reducing errors and possibility to consider human performance with regards to overall safety of a system. The aim of utilising this methodology is to assist an analyst in four main areas: * identify work, actions or tasks within the system which necessitate or essentially depend on human thinking and which are therefore vulnerable to variations in their level of reliability. * identify the surrounding conditions in which the cognition of these situations may be reduced and therefore determine what actions may lead to a probable risk * compile an evaluation from the assessment of the various outcomes of human performance and their effect on system safety – this can then be utilised as part of the probability risk assessment (PRA). * make suggestions as to how identified error producing conditions may be improved and therefore of how the system’s reliability can be enhanced whilst also reducing risk. 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「CREAM」の詳細全文を読む スポンサード リンク
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