Single-Blind Study
A clinical trial where participants do not know whether they are receiving active treatment or placebo, but the researchers do. Single-blinding reduces participant bias but does not eliminate potential investigator bias in outcome assessment.
Technical Context
Single-blind (participant-blind) designs are used when investigator blinding is impractical — for example, when the treatments require different administration procedures that the investigator must perform (different injection techniques, different monitoring requirements). Participant blinding still reduces the placebo effect, reporting bias, and behavioural changes that knowledge of treatment assignment might cause. Single-blind designs are acceptable for some regulatory submissions but are considered weaker evidence than double-blind trials. Blinded outcome assessment (PROBE design — Prospective Randomised Open Blinded Endpoint) can partially compensate for lack of investigator blinding by ensuring outcomes are evaluated by individuals unaware of treatment assignment.