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4. What is the difference between a control group and an experimental group?

	A control group always contains fewer subjects than experimental groups.
	In control groups, the variable under study is manipulated. In experimental groups, the variable under study is not manipulated.
	In experimental groups, the variable under study is manipulated. In control groups, the variable under study is not manipulated.
	Control groups are part of cross sectional designs while experimenal groups are found in longitudinal designs.