If a researcher is conducting a study to compare two treatments for generalized anxiety disorder, and he assigns men to one treatment and women to the other, gender is a(n) because it co-varies with

Confounding variable; the Independent variable.

Explanation:

Confounding variables are the variables that affect the experiment other than the dependent and independent variables. Also, confounding variables may cause a result in the ongoing experiment by affecting independent and dependent variables. It can be controlled by randomization, matching, etc.

Whereas, the Independent variables are the variables that are controlled, changed or manipulated by the experimenter in an experiment. The independent variable directly affects the Dependent variable. The change in the Independent variable directly causes a change in the dependent variable.

answer; software failure, and human error;