Factor (2 of 2)
A factor is a "within-subjects" factor (sometimes called a "within-subjects
variable") if the same subjects are used for each level of the factor.
If in the experiment on drug dosage just discussed, each subject were
tested three times (once with the 50 mg dose, once with the 100 mg dose,
and once with the 150 mg dose) then the variable "drug dosage" would be
a within-subjects factor. There would only be one group of subjects, and
each subject would experience all three levels of the variable (all three
drug dosages). Normally, the treatments are administered in a
or randomized order. Within-subject factors are sometimes
referred to as "repeated-measures" factors since repeated measurements
are taken on each subject.