Promelute Inc., a pharmaceutical company, conducts a study f…

Promelute Inc., a pharmaceutical company, conducts a study for its new drug for the treatment of obsessive-compulsive disorder. The researcher is unclear about the results of the study because he is not sure if the improvement observed resulted from the properties of the drug or from the participants’ expectations about the effect of the drug. Such an effect is known as a(n)________ effect.