What does it mean for the experiment to be placebo controlled?
Show Frequently Asked Questions -------------------------- Daniel J. Simons and Walter Boot *This document provides some definitions and then answers questions about the claims in our paper. If you have questions not addressed in this FAQ or in the paper, please email us.* ---------- Some Definitions ---------------- *Randomized Controlled Trial (RCT)*: A randomized controlled trial is an intervention
study that includes at least one treatment condition and at least one control condition, with participants randomly assigned to the conditions. *Double Blind Design*: In a double blind design, both the participants and the experimenters are kept in the dark about the condition assignment. That is, participants do not know whether they are in a treatment condition or a control condition, and experimenters do not know which participants are in each condition. In a single-blind design, participants
do not know whether they are in the treatment or control condition, but experimenters are aware of the condition assignments. *Placebo-controlled design*: A placebo control condition is one that appears in all respects to be identical to the treatment condition but that lacks the critical ingredient of the treatment. *Active Control*: An active control group is one in which participants engage in some task during the intervention period. Active control groups are not necessarily matched to the
treatment group in any way, and the tasks performed by an active control group might differ in many ways from those performed by the experimental group. *No-Contact control*: A no-contact control group takes the same pre-test and post-test as the treatment group, but does not complete any task during the intervention period (they have no contact with the experimenters). *Waitlist control*: A waitlist control group believes that they will receive the treatment at some later point. Typically, such
participants do not complete the pre-test with the treatment group. They typically do complete the post test. *The gold standard*: The gold standard for an intervention is a double-blind randomized controlled trial with a placebo control group that is matched to the treatment group in all respects except for the treatment. ---------- Frequent Questions and Our Answers ---------------------------------- How can the placebo effect be controlled in an experiment?One strategy for disentangling the placebo effect from these non-specific effects is to include a no-treatment-control (NTC) arm in which a group of participants receives neither placebo nor active treatment.
Is placebo a controlled trial?A placebo is an inactive drug or treatment used in a clinical trial. It is sometimes referred to as a “sugar pill.” A placebo-controlled trial compares a new treatment with a placebo. The placebo is usually combined with standard treatment in most cancer clinical trials.
Is the placebo effect experimental or control?Placebo interventions primarily serve as control treatments in experimental studies, enabling researchers to determine the specific effects of a particular treatment. Clinical investigators use randomized, double-blind placebo-controlled trials as a gold standard to validate treatments.
What is the purpose of placebo controls?Both placebos and controls are used in research studies to prevent the placebo effect, or the real or apparent improvement in a patient's condition due to wishful thinking by the investigator or the patient. Study participants often do not know if they received the study drug or placebo or control group.
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