Test methods terms

Note We have discussed the test procedures and tolerances in general terms. For more accurate test methods and tolerances see lEC 60529. 

Glossary of Terms. Test Methods for Pressure Sensitive Adhesive Tapes, Pressure Sensitive Tape Council, 1996. 

Test method for effects of outdoor weathering on pipeline coatings Definitions of terms relating to corrosion and corrosion testing... 

The relative error is the absolute error divided by the true value it is usually expressed in terms of percentage or in parts per thousand. The true or absolute value of a quantity cannot be established experimentally, so that the observed result must be compared with the most probable value. With pure substances the quantity will ultimately depend upon the relative atomic mass of the constituent elements. Determinations of the relative atomic mass have been made with the utmost care, and the accuracy obtained usually far exceeds that attained in ordinary quantitative analysis the analyst must accordingly accept their reliability. With natural or industrial products, we must accept provisionally the results obtained by analysts of repute using carefully tested methods. If several analysts determine the same constituent in the same sample by different methods, the most probable value, which is usually the average, can be deduced from their results. In both cases, the establishment of the most probable value involves the application of statistical methods and the concept of precision. 

ASTM E177 - 86. Form and Style for ASTM Standards, ASTM International, West Conshohocken, PA ASTM E177 - 86 Standard Practice for Use of the Terms Precision and Bias in ASTM Test Methods. ... 

The front end of this tier approach is a screen, the functional observation battery (FOB) Gad (1982) or Irwin (1968) screen. This is the tool of choice for initial (and for most of the compounds covered by this volume, the only screen tests for) identification of potentially neurotoxic chemicals. The use of such screens, other behavioural test methods, or what are generally called clinical observations does, however, warrant one major caution or consideration. That is that short-term (within 24 hr of dosing or exposure) observations are insufficient on their own to differentiate between pharmacologic (reversible in the short term) and toxicological (irreversible) effects. 

Hardness is essentially a measure of stiffness and in principle can be related to modulus. For plastics, the term hardness refers to resistance to indentation but depending on the test method the measurement is made either with the indentation load applied or after its removal when elastic recovery has taken place. The standard methods are given in ISO 868 (Shore) [6] and ISO 2039 (Ball indentation and Rockwell) [7]. However, Vickers microhardness is more satisfactory for monitoring degradation of rigid materials. 

The uncertainty of a measurement is always a very important consideration but it is especially so with durability tests. In addition to the basic physical test methods, there are the complications of exposure conditions, tests spanning long times and the process of extrapolating results to make predictions. The combination of these factors will inevitably lead to large uncertainties that can very easily be of such a magnitude that any conclusions are meaningless. Terms used to describe precision include repeatability, which refers to within laboratory variation and reproducibility, which refers to variation between laboratories. 

In general terms, the presence of two or more of the structural features indicated above in the same compound will tend to increase the risk. The selection of compound groups and of individually indexed compounds below includes compounds known to have been involved or those with a multiplicity of such structural features which would be expected to be especially susceptible to peroxide formation. A more recent and thorough review of peroxidation risks gives a critical assessment of test methods for peroxides [8],... 

Sampling records for any procedure must be complete and should include, but is not restricted to, items relating to the origin of the sample, methods of storage, analytical tests performed, the test methods used, and the analyst(s) who performed the test methods (Table 6.1). In summary, there must be a means to identify the sample history as carefully as possible so that each sample is tracked and defined in terms of source and activity. Thus, the accuracy of the data from any subsequent procedures and tests for which the sample is used will be placed beyond a reasonable doubt. 

Thus, when a property of the sample (which exists as a large volume of material) is to be measured, there usually will be differences between the analytical data derived from application of the test methods to a gross lot or gross consignment and the data from the sample lot. This difference (the sampling error) has a frequency distribution with a mean value and a variance. Variance is a statistical term defined as the mean square of errors the square root of the variance is more generally known as the standard deviation or the standard error of sampling. 

Interlaboratory or between-laboratory precision is defined in terms of the variability between test results obtained on the aliquots of the same homogeneous material in different laboratories using the same test method. 

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