*4.2. Measurement Comparisons in Other Fields*

This case study considered CCPR comparisons, but in other areas, comparisons may have different general characteristics. For instance, degrees of freedom are usually high in CCPR comparisons and can be ignored; however, in some other areas, they need to be taken into consideration. For instance, in a CIPM key comparison of polychlorinated biphenyl (PCB) congeners in sediment [18], some participants reported very low degrees of freedom (as low as two). The uncertain number format used in GTC also handles degrees of freedom.

The CCPR requires participants in CIPM comparisons to realize their scales independently. Therefore, the results of participants in the initial comparison were not correlated. However, in other areas, the assumption of independence at the CIPM level may not hold. In comparisons involving mass, for example, the lack of independence among participants' scales has to be considered [19]. In the future, if digital reporting were to adopt something equivalent to the uncertain number format, the necessary information about shared influences would be accessible in DCCs. This would once again simplify data analysis and deliver more informative results.
