A study that is set up so that participants do not know which study treatment they are getting, and researchers do not know either.
How to say: Double-blind study
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Some studies are done this way because knowing which treatment each participant is getting can affect the results of the study, through a concept called bias.
Bias can occur when participants or researchers know which study treatment participants are getting.
Participants can ask to find out which study treatment they received after the study ends.