Choose the correct meaning of a double-blind, placebo-controlled experiment. In a double-blind, placebo-controlled experiment, a subject does not know whether he or she received a treatment or an inactive substance. subjects with similar characteristics are assigned to the same group. subjects are assigned to different treatment groups, one of which receives an inactive substance that appears to be a treatment, through random selection. a subject who received an inactive substance reports an improvement in health or behavior. neither the subjects nor the people administering the treatments know who received a treatment and who received an inactive substance.

A double-blind experiment is a type of experiment where both the experimental units and the researchers that analyze the data don't know what kind of treatment was applied to each subject.

This means, that if it is a placebo-controlled experiment. The subjects will be randomly assigned either the medicament to test ("treatment" group) or the placebo ( "control" group) but they will not know which one they are taking. This way the placebo effect is eliminated.

On the other hand, in other to eliminate the observer bias, the researchers will also not know which patient belongs to the "control" group and wich patient belongs to the "treatment" group.

I hope it helps!