Describe two situations in which factorial designs are commonly used

What will be an ideal response?

There are three specific uses of factorial designs that are discussed in the text. (1) A new study can be built by adding a new factor to an earlier research study. (2) A participant characteristic such as age or gender can be used as a second factor to separate participants into more homogeneous groups and reduce variability in a between-subjects design. (3) The order of treatments can be used as a second factor in a counterbalanced within-subjects design to measure the order effects.