A third factor that produces an apparent relationship between two variables is called a:

1. Two variables can move together without either causing the other. 2. While variables are sometimes correlated because one does cause the other, it could also be that some other factor is actually causing the systematic movement in our variables of interest. 3. That other factor is a confounding variable. 4. Random assignment in an experiment is the standard defence against it. _Source: OpenStax Psychology 2e (CC BY 4.0), Ch 2 'Psychological Research', sections 2.1-2.4_