Ch. 8: EXPERIMENTAL DESIGN

Important Terms

You should know the definitions of the following terms. You should also be able to apply these concepts (i.e., recognize examples of them in several contexts and use them to critically evaluate a study, as well as apply them in the design of your research proposal).

balanced Latin square
baseline
between-subjects design
carryover effects
control condition
counterbalancing
individual differences
internal validity
Latin-square design
matching
randomization
subject attrition
within-subject design

INTERNAL VALIDITY IN EXPERIMENTS

This chapter continues the subject of designing experiments that are internally valid--i.e., ones in which the differences in the DV can reasonably attributed to (caused by) the different levels of the IVs. The good news here (I always have good news!) is that there is only one major issue in this chapter: the decision between a "between-subjects" vs. a "within-subjects" experimental design in planning an experiment. This is an important choice, as illustrated by the invalidity of the "executive monkey" study due to one of the problems associated with the between-S design employed (nonequivalence of Ss in the two conditions). The chapter discusses the relative advantages/disadvantages of the two types of designs (I often call this the yin-yang of research design, because the advantages of one are simultaneously the disadvantages of the other, and vice-versa. As usual, your authors present solutions to some of the problems associated with each design, as well as factors that should be considered in making the decision to use a Between-S or Within-S design.

EXPERIMENTAL DESIGN

CONTROL CONDITIONS

CHOOSING AN EXPERIMENTAL DESIGN