In a blind experiment,sample members do not know whether they are part of an experimental group or a control group. In a double-blind experiment, neither sample members nor researchers conducting an experiment have such information.
See solution.
Practice makes perfect
We want to determine the difference between a blind experiment and a double-blind experiment. First, let's describe both types of experiments using an example. Assume that we want to determine whether a new painkiller works. We will need three groups of individuals — researchers conducting the study, an experimental group, and a control group.
If sample members do not know whether they are part of an experimental group or a control group, we have a blind experiment. By using this type of experiment we avoid, for example, a situation in which members of experimental group could feel better only because they were aware that they took a real painkiller.
Do They Know Who Is in Which Group?
Sample Members
Researchers
Blind Experiment
No *
Yes ✓
Double-blind Experiment
?
?
Next, if researchers know who is taking a real painkiller and who is not, they could look differently at the symptoms reported by a person from a particular group. To avoid that kind of situation we can use a double-blind experiment in which neither sample members nor researchers have such information.
Do They Know Who Is in Which Group?
Sample Members
Researchers
Blind Experiment
No *
Yes ✓
Double-blind Experiment
No *
No *
Notice that a double-blind allows us to avoid two types of biases.
