Based on the relationship between one variable and the others, kinds of research variables can be divided into five:
1. Independent Variable
This variable is often called as stimulus, predictor, and antecedent variable. In Indonesian language, it is often referred to independent variable, affect variable. Independent variable is variable that affects or become the cause of the changes or presence of dependent variable.
2. Dependent Variable
This variable is often called as output, criteria, and consequent variable. In Indonesian language, it is often referred to dependent variable, affected variable. Dependent variable is the variable that is affected or become the consequence, because of the independent variable.
3. Moderator Variable
This variable is often called second independent variable. Moderator variable is variable that affects (Strengthening and weakening) the relationship between independent and dependent variables.
4. Intervening Variable
Tuckman (1988) stated that "“An intervening variable is that factor that theoretically affect the observed phenomenon but cannot be seen, measured, or manipulated”. Intervening variable is variable that theoretically affects the relationship between independent and dependent variables, but cannot be observed and measured. This variable is often called mediating variable, intermediary variable. This variable is located between independent variable and dependent variable, so that independent variable does not directly affect the change or the presence of dependent variable.
5. Control Variable
Control variable is variable that is controlled or held constant, so that the relationship between independent and dependent variables is not influenced by external factors that are not examined. Control variable is often used by researchers, when they will conduct a comparative study through experimental research.
