Subjective judgment, reliability

Visible symptoms are useful in characterizing the response of vegetation to a variety of stresses, including air pollution/ Similar symptoms, induced by different stresses, have been well described and may confuse the diagnosis. On the basis of studies to date, diagnostic techniques that use indicators other than visible injury (e.g., respiration) are less reliable than the subjective judgment of an experienced observer. Thus, it is important that researchers become familiar with injury symptoms caused by oxidants and those caused by other stresses. This section briefly describes the injury symptoms used for diagnostic purposes. 

Baber and Kang s method for estimating industry-level IRRs is itself subject to measurement error, so the reliability of the measured rates of return for each industry group (pharmaceuticals and controls) is uncertain. Nevertheless, Baber and Kang applied the estimation method consistently across all firms in the three groups, so the differences in profit rates between pharmaceuticals and controls, which were stable across a wide range assumptions about their investments, are, in OTA s judgment, reliably estimated. 

Reliability is not a property of the instruments, but of the entire measurement process. This includes the tools, the instruments, the procedures, and the people. Subjective judgment can be very reliable in some... 

Humans are sensitive to moisture and can reliably describe the humidity of the environment using word scales as demonstrated in Fig. 5.12. The subject s humidity judgments appear to be functions of the air s dew point, a measure of absolute humidity, and are relatively unaffected by the ambient temperature. Further, people are also good at perceiving skin moisture, as illustrated in Fig. 5.13, where perceived skin wettedness is seen to correlate well with measured skin wettedness. 

Such definitions imply that there is a reliable test for rancidity, but this is not the case. The difficulties are centered about the fact that in the final analysis, rancidity must be detected through organoleptic observation, which is subject to all the weaknesses inherent in a test involving personal judgment. As was pointed out in a recent discussion (S), these weaknesses include variabilities in the taste and odor sensitivities of persons in the same or different laboratories, their previous taste experiences, the prevailing condi-... 

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When the question of reliability of written records enters into a search, critical evaluation rests mainly with the investigators who use the search findings, particularly in patent searches. What may appear to the searcher as a mere oddity or even an error may be something truly new. Judgment on the matter is the prerogative of the subject-field expert. 

In summary, we obtain degrees of belief for one question (i.e.. Will John reach the bus in time ) from probabilities for another question (i.e.. Is the alarm clock reliable ). Dempster s rule begins with the assumption that the questions for which we have probabilities are independent with respect to our subjective probability judgments, but this independence is only a priori it disappears when conflict is discerned between the different items of evidence. 

Not that every scientist was competent to judge every contribution. The network solved that problem too. Suppose Scientist M announces a new result. He knows his highly specialized subject better than anyone in the world who is competent to judge him But next to Scientist M are Scientists L and N. Their subjects overlap M s, so they understand his work well enough to assess its quality and reliability and to understand where it fits into science. Next to L and N are other scientists, K and O and J and P, who know L and N well enough to decide whether to trust their judgment about M. On out to Scientists A and Z, whose subjects are almost completely removed from M s. 

In summary it must be borne in mind that the necessary judgments introduce a subjective element into the determination of reliability data. However, this is unavoidable. Therefore, it is essential that the judgments are exercised with a background of profound knowledge of plants, processes and components. 

In descriptive analysis small groups of highly trained judges with considerable experience with the commodity under study develop adjectives to characterize the qualitative properties of the product (attributes like appearance, aroma, texture, taste, etc., are analyzed). The data of sensory analysis experiments are subjected to statistical analysis to get reliable results. Instrumental methods are also used to correlate physicochemical measurements with sensory judgments (Table 5). 

These methods are based on subjective opinions obtained from company executives and consumers. These methods are ideally suited for forecasts where there are no past data or past data is not reliable due to the changes in environment (e.g., peacetime data on spare part needs for military aircrafts are not useful for forecasts during war time). Qualitative methods are commonly used for strategic decisions where long-term forecasts are necessary. The qualitative approaches vary in sophistication from scientifically conducted consumer surveys to intuitive judgments from top executives. Quite frequently qualitative methods are also used as supplements to quantitative forecasts. In a 1994 survey of forecasting in practice, 78% of top 500 companies responded that they always or frequently used qualitative methods for forecasting (Sanders and Manrodt, 1994). 

Communication of the human operator with the process he has to control is very important. To provide automatic responses to each and every demand made by the process would be economically impracticable and also undesirable from the point of view of reliability of the system. Human intervention remains necessary, subject to the condition that it does not impose too heavy a strain on the operating personnel involved. The control system must meaningfully select, prepare and present the requisite information from the process, so that even in critical phases of operation no wrong interventions due to overburdening of human judgment and response capacity will occur. 

Many investigators have traditionally avoided the use of statistical techniques because the added reliability did not seem to offset the effort and time required to become familiar with the methodology or to perform the necessary calculations. Most often, the results must be interpreted in terms of relative rankings. Such interpretations can be subjective and depend much on the judgment of the investigator. 

The reason for such diversity in methods of determining SILs is probably due to the difficulties of arriving at reliable and credible estimates of risk in the wide variety of situations faced in industries. Whilst a quantitative risk assessment is desirable it may be worthless if the available data on fault rates is minimal or subject to huge tolerances. Qualitative methods allow persons to use an element of judgment and experience in the assessment of risk without having to come up with numerical values that are difficult to justify. 

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