What characteristic distinguishes a randomized block design?

A randomized block design is distinguished by the process of grouping experimental units into blocks based on certain characteristics that are relevant to the response variable. The purpose of blocking is to control for the variability among the experimental units. In this design, researchers first identify factors that may influence the outcome and then create blocks that are homogeneous with respect to those factors. After the blocks are formed, randomization occurs within each block, allowing for a more precise estimation of treatment effects by minimizing the impact of extraneous variability.

This method enhances the ability to detect effects of treatments since it accounts for potential confounding variables. Consequently, the randomized block design leads to more reliable conclusions about the treatments being tested, as it effectively reduces the noise in the data that could obscure true treatment effects. The other options do not capture this essential characteristic of blocking prior to randomization, which is foundational to the effectiveness of the design.