Placebo control primarily helps isolate which type of effects?

• A. Observational bias
• B. Ethical considerations
• C. Expectation effects
• D. Statistical errors

Answer: (C)

Expectancy effects are what placebo controls help isolate. In a placebo-controlled study, participants (and often researchers) don’t know who receives the real treatment, so expectations about improvement are balanced across groups. If the real treatment leads to more improvement than the placebo after this balance, that difference reflects the treatment’s actual effect rather than belief or anticipation. This is why placebo controls are used to separate expectancy-related responses from the treatment’s true effect. Other issues like observational biases, ethical questions about deception, or statistical errors aren’t the primary focus of this control in this context.