A research subject improves after receiving an inert treatment they believe is active. This best illustrates which phenomenon?

Improvement attributable to the expectation of benefit from an inactive treatment is the placebo effect, which is why blinded, placebo-controlled designs are used.Other options: Selection and recall bias are study-design biases; regression to the mean is a statistical artifact, not belief-driven improvement.Key exam takeaway: Placebo effect = improvement from expectation; controlled with blinding and placebo arms.