In a single-blind study, who knows the makeup of the test and control groups?

In a single-blind study, it is the experimenters who have knowledge of which participants are receiving the treatment and which are in the control group. This design ensures that the participants, or subjects, do not know to which group they belong, preventing any potential bias in their responses or behaviors based on their knowledge of the treatment.

The primary purpose of keeping the subjects unaware of their group assignment is to minimize the influence of their perceptions and expectations on the study's outcomes. If the subjects were aware of their group assignment, their behavior might be unconsciously altered, potentially skewing the results. On the other hand, the experimenters need to know the group makeup to properly administer the treatment and assess the outcomes accurately.

In a single-blind design, while observers and independent evaluators may also be part of the study, their roles do not negate the specific control that experimenters have regarding the knowledge of group assignment. This clear distinction is crucial in maintaining the integrity of the study and ensuring that the analysis of results remains objective and reliable.