Like graph theory, design theory is probably not what any non-mathematician might expect from its name. When researchers conduct an experiment, errors can be introduced by many factors (including, fo...Like graph theory, design theory is probably not what any non-mathematician might expect from its name. When researchers conduct an experiment, errors can be introduced by many factors (including, for example, the timing or the subject of the experiment). It is therefore important to replicate the experiment a number of times, to ensure that these unintended variations do not account for the success of a particular treatment.