Factor (1 of 2)
A factor is an independent variable
an experiment is testing the effect of drug dosage, then "drug
dosage" is a factor. Some experiments have more than one factor. For
example, if the effect of drug dosage and age were both manipulated
in the same experiment, then these two variables would be factors.
The experiment would be called a two-factor experiment.
A factor is a "between-subjects" factor (sometimes called a
"between-subjects variable") if a different group of subjects is used
for each level
of the factor. For
instance, consider an experiment comparing three levels of drug
dosage (50 mg, 100 mg, and 150 mg). If the 50 mg dose were given to
one group of subjects, the 100 mg dose to a second group, and the 150
mg dose to a third group, then a different group of subjects would be
used for each level of the factor "drug dosage." This would make drug
dosage a between-subjects factor.