ISO 5725-2:1994 pdf download -Accuracy (trueness and precision) of measurement methods and results – Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method.
5.1.2 The Derformance of these measurements shall organized and instructions issued as follows. Any preliminary checking of equipment shall be as specified in the standard method. Each group of n measurements belonging to one level shall be carried out under repeatability con- ditions, ¡.e. within a short interval of time and by the same operator, and without any intermediate recalibration of the apparatus unless this is an in- tegral part of performing a measurement. It is essential that a group of n tests under re- peatability conditions be performed independently as if they were n tests on different materials. As a rule, however, the operator will know that he/she is testing identical material, but the point should be stressed in the instructions that the whole purpose of the experiment is to determine what differences in results can occur in actual testing. If it is feared that, despite this warning, previous results may influence subsequent test results and thus the repeatability variance, it should be considered whether to use n separate samples at each of the 4 levels, coded in such a way that the operator will not know which are the replicates for a given level. However, such a pro- cedure could cause problems in ensuring that re- peatability conditions will apply between replicates. This would only be possible if the measurements were of such a nature that all the qn measurements could be performed within a short interval of time.
5.1.3 In 5.1.2 and elsewhere in this part of IS0 5725, reference is made to the operator. For some measurements, there may in fact be a team of operators, each of whom performs some specific part of the procedure. In such a case, the team shall be regarded as “the operator” and any change in the team shall be regarded as providing a different “op- erator”. 5.1.4 In commercial practice, the test results may be rounded rather crudely, but in a precision exper- iment test results shall be reported to at least one more digit than specified in the standard method. If the method does not specify the number of digits, the rounding shall not be coarser than half the repeatabil- ity standard deviation estimate. When precision may depend on the level m, different degrees of rounding may be needed for different levels. 5.2 Recruitment of the laboratories 5.2.1 The general principles regarding recruitment of the laboratories to participate in an interlaboratory experiment are given in 6.3 of I S 0 5725-1 :1 994. In enlisting the cooperation of the requisite number of laboratories, their responsibilities shall be clearly stated. An example of a suitable enlistment question- naire is given in figure 1. 5.2.2 For the purposes of this part of I S0 5725, a “laboratory” is considered to be a combination of the operator, the equipment and the test site. One test site (or laboratory in the conventional sense) may thus produce several “laboratories” if it can provide several operators each with independent sets of equipment and situations in which to perform the work.