This is so much error of measurement that any effects of the independent variable are obscured. As a result the effects of the IV may be obscured, especially when it is a weak variable. Just because a variable is a weak one does not mean that it is unworthy of study. The societal importance of certain weak variables may be great. Can be represented pictorially through the use of boxes.
Simplest design involves one experimental group and on control group.
Manipulation through events is the technique of choice. Since nonlinear carry over effects cannot be controlled, a Between Subjects design is recommended instead of a Within Subjects Design. Remedy for Sequencing Effects Counterbalancing Intrasubject counterbalancing Used with single subject design. Complete counterbalancing All combinations of orders are used. A different subject is used for each order.