Statistical Consequences in the Assurance of Measurement Compatibility

Of these 42 papers, 13 came from countries within the EU, eight from European coimtries outside the EU, and 12 from North America. He mentioned that the papers dealing with the use of CRMs did not make reference to any user guide such as ISO Guide 33 (1989) (see Section 1.2) and further that the comparison between the found results and the certified means and intervals are often presented in rather vague, or non statistical terms . 

The reasons for such vagueness may lie in a combination of factors, the lamentable level of proper understanding of statistics amongst many analysts and, as mentioned above, the inconsistent and complex manner in which many certification bodies use statistics to produce their certified values and the willingness of journals to accept papers that lack proper validation of restdts and do not describe the proper use of CRMs. 

In this Section we aim to make the CRM user aware of the uncertainty budgets that need to be considered with the use of CRMs. Certified values in CRMs are the property values (mass fraction, concentration, or amount of substance) and their uncertainty, the uncertainty being in many instances a specified confidence interval for the certified property. As we discussed before, this uncertainty value is not always a complete uncertainty budget for an analytical process from sampling to production of data. But even when disregarding the subtle differences in the certificates, the way a CRM is used has serious consequences on the uncertainty budget that has to be applied to a user s result. This is summarized in Table 7.2. These uses may affect accuracy claims as well as traceability claims. It is the user s obligation to establish com- 

Matrix Match Matrix Related Matrix Relation Inferred Matrix Not Related 

Only useable with truly matrix-independent procedures Control Measurement 

---