A single-blind study is a type of research design where the participants do not know whether they are receiving the treatment or a placebo. This helps to reduce bias in their responses, as they are unaware of which group they belong to. The researchers, however, do know which participants are receiving the actual treatment, allowing them to monitor the effects accurately. This method is commonly used in clinical trials to test the effectiveness of new medications or therapies. By keeping participants blind to their group assignment, researchers can obtain more reliable data on how the treatment works, minimizing the influence of participants' expectations on the results.