Blocking is a method in statistics used to reduce the effect of nuisance variables in an experiment. Nuisance variables are those factors that could result in variations during the experiment. During blocking, subjects with similar features are grouped in the same block, and treatment is then administered to each of these subjects. In order to form blocks, blocking factors are used.
Blocking factors can affect the results of an experiment but they are of no importance to the experimenter. An example of a blocking factor is age. So, for Isamu who seeks to use blocking to deal with an extraneous factor in his experiment, blocking would enable him to divide his subjects into groups based on similarities.
