Nuisance Variable

A nuisance variable is an unwanted variable that is typically correlated with the hypothesized independent variable within an experimental study but is typically of no interest to the researcher. It might be a characteristic of the participants under study or any unintended influence on an experimental manipulation. A nuisance variable causes greater variability in the distribution of a sample’s scores and affects all the groups measured within a given sample (e.g., treatment and control).

Whereas the distribution of scores changes because of the nuisance variable, the location (or the measure of central tendency) of the distribution remains the same, even when a nuisance variable is present. Figure 1 is an example using participants’ scores on a measure that assesses accuracy in responding to simple math problems. ...