reference laboratory prepares a suitable number of objects that are as identical as possible, and sends them all at the same time to the participating laboratories, and often the objects are samples of a product or material, and the reference laboratory is confronted with the difficult task of ensuring sufficient homogeneity of the samples, and sometimes, when this scheme is used, the object has no previously determined reference value, mõõteskeem, mille kohaselt valitakse rida mõõteobjekte (proove), mida mõõdetakse või analüüsitakse paljudes laborites enam-vähem samaaegselt korratavustingimustel