Editing Blinded experiment (section)

{{short description|Experiment in which information about the test is masked to reduce bias}}
In a '''blind''' or '''blinded experiment''', information which may influence the participants of the [[experiment]] is withheld until after the experiment is complete. Good blinding can reduce or eliminate experimental [[bias]]es that arise from a participants' expectations, [[Observer-expectancy effect|observer's effect on the participants]], [[observer bias]], [[confirmation bias]], and other sources. A blind can be imposed on any participant of an experiment, including subjects, researchers, technicians, data analysts, and evaluators. In some cases, while blinding would be useful, it is impossible or unethical. For example, it is not possible to blind a patient to their treatment in a physical therapy intervention. A good [[clinical protocol]] ensures that blinding is as effective as possible within ethical and practical constraints.

During the course of an experiment, a participant becomes [[#Unblinding|unblinded]] if they deduce or otherwise obtain information that has been masked to them. For example, a patient who experiences a side effect may correctly guess their treatment, becoming unblinded. Unblinding is common in blinded experiments, particularly in pharmacological trials. In particular, trials on [[pain medication]] and [[antidepressants]] are poorly blinded. Unblinding that occurs before the conclusion of a study is a source of experimental error, as the bias that was eliminated by blinding is re-introduced. The [[Consolidated Standards of Reporting Trials|CONSORT]] reporting guidelines recommend that all studies assess and report unblinding. In practice, very few studies do so.<ref name=Bello2014>{{cite journal |last1=Bello |first1=Segun |last2=Moustgaard |first2=Helene |last3=Hróbjartsson |first3=Asbjørn |title=The risk of unblinding was infrequently and incompletely reported in 300 randomized clinical trial publications |journal=Journal of Clinical Epidemiology |date=October 2014 |volume=67 |issue=10 |pages=1059–1069 |doi=10.1016/j.jclinepi.2014.05.007 |pmid=24973822 |issn=1878-5921}}</ref>

Blinding is an important tool of the [[scientific method]], and is used in many fields of research. In some fields, such as [[Evidence-based medicine|medicine]], it is considered essential.<ref>{{cite web|url=http://www.cebm.net/oxford-centre-evidence-based-medicine-levels-evidence-march-2009/|title=Oxford Centre for Evidence-based Medicine - Levels of Evidence (March 2009) - CEBM|date=11 June 2009|website=cebm.net|archive-url=https://web.archive.org/web/20171026195451/http://www.cebm.net/oxford-centre-evidence-based-medicine-levels-evidence-march-2009/|archive-date=26 October 2017|url-status=live|access-date=2 May 2018}}</ref> In clinical research, a trial that is not a blinded trial is called an [[open-label trial|open trial]].