For the comparison of a measured quantity of a test object with that of a reference standard, various sequences of repeated measurements and various methods for the evaluation of measurement results are possible. A measurement cycle, consisting of a certain number of single measurements and leading to a value for the difference between a test object and a standard, may have common data with subsequent cycles. In this case, in which cycles are correlated to one another, the uncertainty calculation must take covariances into account. The paper presents the uncertainty calculation for the often-used correlated RTR cycle as well as for any cycle in general. Finally the efficiencies of selected cycles are presented and discussed.
