Promelute, a pharmaceutical company, conducts a research on participants for its new drug for obsessive-compulsive disorder. but the experimenter is unclear about the conclusions of the study because he is not sure if the improvement has been caused by the properties of the drug or by the participants' expectations about the effect of the drug. such an effect is known as a(n) effect.

Such an effect, in which  the experimenter is unclear about the conclusions of the study because he is not sure if the improvement has been caused by the properties of the drug or by the participants' expectations about the effect of the drug  is known as a placebo  effect.
Placebos do not contain an active substance meant to affect health. They can sometimes improve a patient's condition simply because the person has the expectation that it will be helpful.

A. all judges are appointed at the state and federal levels