What is the difference between an extraneous variable from a nuisance variable?
Extraneous Variables: any variable, other than the IV or DV EV’s can become a problem if they can take on more than one value AND the values of the EV are systematically different across the levels of the IV. In this case, the EV has become a confound. Ideally, in experiments, EVs will only have one value. As such, they cannot become confounds. If the EV can take on different values and we suspect that they could become systematically different across the levels, we will have to find some other way of controlling them. Nuisance variables are extraneous variables which do not systematically differ between the levels of the IV (i.e.
