Some design-problems in crop experimentation .1. the use of blocks

Field experiments are commonly designed in blocks and there are sound reasons for using them, for example, control of unwanted environmental differences and administrative convenience. If used, they should be chosen to correspond to perceived differences in the site or to simplify farm operations and not merely to conform to statistical desiderata. Thus, it is not essential that each must contain one plot for each treatment, though there are advantages if they do. Some of the consequences of using other block sizes are examined, it being borne in mind that modern computer packages will perform most of the tiresome arithmetic. The effectiveness of blocks is considered and it is noted that they sometimes do harm rather than good. The analysis of variance is explained in terms of strata as used in many modern computer programs and is extended to include the recovery of information and resolvability. Recommendations are made as to randomization.