What term describes a control treatment that is identical to the experimental treatment except for the critical item being studied?

The term that best describes a control treatment identical to the experimental treatment except for the critical item being studied is "placebo." In experimental research, especially in clinical trials, a placebo is used to provide a comparison against the effect of the treatment. It mimics the experimental treatment in every way except for the active ingredient or critical item being tested. This allows researchers to assess the true effectiveness of the treatment by controlling for participants' expectations and other psychological factors.

In contrast, the term "control group" generally refers to a group that does not receive the experimental treatment at all, making it distinct from the placebo, which still involves the administration of a treatment that is identical to the experimental treatment. "Variable analysis" refers to examining the relationships between variables and does not describe a treatment type. "Intervention" refers to the application of a treatment or program designed to bring about change but does not specifically define the nature of a control treatment in comparison to an experimental one.