Question

what is the purpose of blocking in experimental design?

Answer 1

the control for multiple variables in a experiment

Answer 2

In statistics, blocking reduces known variability. If say, we have multiple groups of people in a study, and we *know* that a certain group has a specific tendency that will alter the results of the study, we can separate these two groups, and subject them to the same study. Then we will see what effect this tendency had on the results of the study by comparing each group to a control group. I'm trying to be general in my response, but does it make sense?