Used to balance out impact of order effects in repeated measures design (involves making sure each condition comes first/second in equal amounts) i.e. allows for order effects to be distributed evenly across both conditions
Allocating pps. to experimental groups/conditions so pps. have an equal chance to take part in each condition (allows even distribution of pp. characteristics across conditions to avoid extraneous variables)
Using exactly the same formalised procedures and instructions for all participants so individual experience does not become a confoundingvariable and i.e. enable replication
addresses issue of experimenterbias as standardised procedures includes standardisedinstructions that are the same for all pps. i.e. deals with investigator effects