Question

David and alexandra both take part in a research study that is investigating the effects of sleep deprivation on reaction time. david is kept awake for 24 hours straight, while alexandra follows her normal sleep routine. in this study, david is part of which group?

Answer 1

The answer is experimental group
In every study, the subjects would be divided into experimental group and control group 
Experimental group filled with subjects that are forced into a certain situation (by giving them a certain drugs or forcing them the do something)
While the control group filled with subjects that does not receive the treatment that experimental group had (usually by giving them placebo or told them to act normally)