What Are Experimental Groups? Groups in Experimental Design

What Is a Control? A control group in a scientific experiment is a group separated from the rest of the experiment where the independent variable being tested cannot influence the results. This isolates the independent variable's effects on the experiment and can help rule out alternate explanations of the experimental results. http://chemistry.about.com/od/chemistryterminology/a/What-Is-A-Control-Group.htm

What is a Constant Variable? A constant variable is the variable that is held steady for a certain experiment. For example the constant variable may be the temperature held to 180 degrees for the length of the experiment. http://answers.ask.com/science/other/what_is_a_constant_variable_in_science

What Is an Independent Variable? Independent variables are the variables that the experimenter changes to test their dependent variable. For example, a scientist is testing the effect of light and dark on the behavior of moths by turning a light on and off. The independent variable is the amount of light and the moth's reaction is the dependent variable. http://chemistry.about.com/od/chemistryterminology/a/What-Is-An-Independent-Variable.htm

What Is a Dependent Variable? The dependent variable is 'dependent' on the independent variable. As the experimenter changes the independent variable, the change in the dependent variable is observed and recorded. For example, a scientist is testing the effect of fertilizer on the growth of plants by measuring different amounts of fertilizer. Change is growth may occur. The independent variable is the amount of fertilizer and the plant’s growth is the dependent variable. http://chemistry.about.com/od/chemistryterminology/a/What-Is-A-Dependent-Variable.htm