Participant Variables (Subject Variables)
Participant variables (also known as subject variables) are the differing individual characteristics of participants in an experiment. These variables are plentiful and varied including things such as age, background, socioeconomic status, current mood, how much sleep the individual person got the night before, and many more. Participant variables can be considered extraneous variables because they are variables that can influence the results of an experiment but that the experimenter is not studying. These can challenge the validity of a study by influencing the results.