Modifies a noun

• trial: In a single-blind trial, the doctors know which people receive the placebo.

• study: A randomized, single-blind study over 6 months was performed at six specialist centers in Europe.

• placebo: Efficacy of low power laser therapy in fibromyalgia: a single-blind, placebo controlled trial.

• design: Manual acupuncture at traditional and sham points was applied to 20 healthy male students in a single-blind crossover design.

• group: Abstract: DESIGN: A single-blind parallel group randomized controlled trial of 12-week duration, followed by a 4-week cross-over phase.