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
voluntary response bias

9.4.34  question   to estimate the height of a stone  figure, an observer holds a small square up to her eyes and walks backward from the figure. she stops when the bottom of the figure aligns with the bottom edge of the  square, and when the top of the figure aligns with the top edge of the square. her eye level is 1.811.81 m from the ground. she is 3.703.70 m from the figure. what is the height of the figure to the nearest hundredth of a  meter?