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.

Placebo effect

Explanation: Placebo effect is the experience of positive outcome due to expectations.

It is a phenomenon where one's brain convince the body that an inactive substance (like diluted sugar, sterile water) taken or consumed can lead to a relief from an ailment or that a sham treatment can lead to a relief from an ailment which in turn truely cause a relief from the ailment, not because of the inactive substance taken or the sham treatment taken but because of how the brain stimulates the body chemically to believe it actually works.

Such effect is known as the placebo effect.

they all focused on themes about the inevitability of death.