Which type of variable is described as affecting the dependent variable without being the focus of study?

A confounding variable is one that can influence the dependent variable in such a way that it can obscure the true relationship being studied. In research, when a confounding variable is present, it becomes difficult to determine whether the independent variable (the one being manipulated to observe its effects) is truly having an effect, or if the observed changes in the dependent variable are actually due to the confounding variable. This can lead to misleading conclusions if not properly controlled, thus it is essential in research design to identify and manage these confounding variables to enhance the validity of the study's results. They are not the primary focus of the research but can significantly impact the findings, making it crucial to account for them in any experimental design.