singleblind

Single-blind is a methodological term used in experiments, especially randomized controlled trials, to describe a design in which one party—typically the participants—are unaware of which intervention they receive. In many standard descriptions, the researchers or clinicians who administer treatments and collect outcomes know the assignments, so the study is not fully blinded. Some literature, however, uses the term to indicate that outcome assessors are blinded while participants are not; terminology can vary across disciplines.

Purpose and rationale: Blinding aims to reduce biases arising from participants' expectations and behavior, such as placebo effects, and helps produce more reliable comparisons between interventions.

Implementation and challenges: Achieving single-blindness often relies on identical placebo controls or sham procedures. It can be difficult to maintain if side effects reveal allocation. Unblinding may occur, and if assessors are not blinded, detection bias can still arise.

Relation to other designs: The stronger form, double-blind, blinds both participants and investigators or assessors. Open-label trials have no blinding. Triple-blind trials hide allocation from participants, clinicians, and outcome assessors. Blinding is complemented by allocation concealment and standardized assessment tools.

See also related concepts include blinding in clinical trials, double-blind designs, open-label trials, and randomized controlled trials.