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...

Extracted text: 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 effect of a treatment unit The placebo effect A control group Sampling error O Voluntary response bias