Consensus value

FIGURE 21.3 % J and % values for the components of the mitochondrial electron transport chain. Values indicated are consensus values for animal mitochondria. Black bars represent %r red bars,. ... 

To obtain consensus values for specimens which, when certified values are not known, may be used as surrogate CRMs. 

Mean from test procedures within 95% confidence intervals of consensus value of reference material, or >the lower 95% confidence level of the reference procedure... 

When we have evaluated all the rules, an output variable might belong to two or more fuzzy subsets to different degrees. For example, in the enzyme problem one rule might conclude that the rate is low to a degree of 0.2 and another that the rate is low to a degree of 0.8. In aggregation, all the fuzzy values that have been calculated for each output variable are combined to provide a consensus value for the membership of the output variable in each... 

Systematic error is also known as bias. The bias is the constant value difference between a measured value (or set of values) and a consensus value (or true value if known). Specificity is the analytical property of a method or technique to be insensitive to interferences and to yield a signal relative to the analyte of interest only. Limit of reliable measurement predates the use of minimum detection limit (MDL). The MDL... 

The results obtained by various calibrations in the determination of nickel and copper are shown in Tables 1.2 and 1.3. Table 1.4 gives the differences between sampling devices for copper, as determined by each participant, when these are significant at the 95% and 90% levels of confidence. Only the results of participants that had acceptable analytical performance, as measured by precision and agreement with contemporary consensus values for deep North Atlantic waters (Table 1.5), were used for drawing conclusions. 

A consensus value is the easiest and cheapest method for obtaining the assigned value. It is the appropriate approach when all participants are using a single standardized empirical method and a large number of laboratories are involved. 

Currie, L. A., Polach, H. A., Exploratory Analysis of the International Radiocarbon Cross-Calibration Data Consensus Values and Interlaboratory Error, Proceedings of the 10th International Radiocarbon Conference, Radiocarbon. 22, 933... 

NOTE The fraction modern (fm) listed is the consensus value reported by the directors of the studies. (See Appendix E for information about obtaining these materials.)... 

Most of the reference materials discussed are based on natural matrices (seawater, algal cells, sediment) and would initially only be certified for a limited number of constituents. Nevertheless, it is apparent that such materials provide a resource for the investigation of a much wider variety of constituents, and it is important that the ocean science community be encouraged to investigate these materials further. In particular, the existence of these materials would facilitate a wide variety of necessary interlaboratory method comparisons that have been neglected to date. Eventually these intercomparisons will result in consensus values for other constituents, which can then be assigned to the reference materials. 

All of these sediment reference materials would provide stable homogeneous materials containing a wide variety of chemical constituents that could be studied at the discretion of the ocean sciences community, and may ultimately be assigned consensus values for a number of important additional organic and inorganic analytes. 

Consensus Value (of a given quantity) For a reference material, the... 

Other classes of reference materials now in existence include secondary reference materials. These are materials produced commercially for reference purposes, but whose guarantee rests soley with the producer. "Analyzed" materials such as geological materials obtained from the United Staes Geological Survey, represent test samples that complement the variety available from the previously mentioned sources. However, the "accepted" analyses reported for these materials are based upon consensus values obtained from large scale interlaboratory collaborative tests (round robins). Analysis of these materials can provide a useful means of comparing performance with other laboratories, but it does not ensure accuracy. In addi-... 

Lion, one must be cautious of assessing accuracy by comparing results with consensus values because they are often computed Incorrectly in the literature. The quoted values may be based upon averages of all methods without regard to systematic bias that characterizes some methods of analysis. 

If a corrvention method" (an empirically defined method) Is used, the consensus value is the only possibility... 

But this method also has disadvantages. The consensus value could be seriously biased, if the majority of the participants have biased values in the same direction, which could be the case e.g. in the analyses of highly volatile substances. 

Consensus value might be seriously biased (e g. analyses of highly volatile siiistances)... 

Care should be taken to decide whether a consensus value really is good choice... 

Methods to Calculate Consensus Value - Arithmetic Mean... 

If a consensus value is used as the assigned value there are different possibilities to calculate it. If the arithmetic mean is used, an outlier test is required. But in many eases these tests are not very satisfaetoiy, espeeially if several outliers are present. If the tests are strietly used, they ean only be apphed to normally distributed data, whieh is usually not the case in trace analysis. 

---