The paper deals with the examination of the relative efficiency of two mixed designs with reference to the accuracy of comparisons estimation of treatment parameters. One of the designs is called a split-plot × split-block design whereas the second one a split-block-plot design (strip-split-plot design). Contexts in which the designs are equally efficient and when one of them is more efficient than the other one are presented.

Mixed designs, Relative efficiency, Split-block-plot design, Split-plot × split-block design, Strip-split-plot design