From 2003 to 2007, a group of doctors studied the effects of a new attention deficit disorder medication on adults. To compare results, the doctors gave half their patients the new medication and maintained the other half of their patients on their current medication. What is being used in this example?

The placebo effect, because one group believes they are receiving a new prescription but they are actually taking the same prescriptions they always have. This can also be called a single blind experiment because the test subjects do not know which group they are in (or that there are two groups most likely), but the psychologist (s) know who is taking which prescription/who is in which group.