What are the differences between true experimental and descriptive research in terms of procedures in the control of variables?
The significant difference between true experimental research and descriptive research is that only when using experimental research do we manipulate variables. In contrast, when using descriptive research, we do not manipulate variables but rather observe natural behavior.
There are two variables in a research design: the independent variable and the dependent variable. The independent variable is the variable that is manipulated, either by an external "force" or as a "force" itself, to derive experimental results (The Office of Research Integrity, "Elements of Research"). The dependent variable is the variable that is influenced by the independent variable. NC State University provides us the example of conducting an experiment to see how stress affects heart rate. The independent variable would be stress, while the dependent variable would be heart rate. The researcher can gradually increase stress levels, which are assumed to influence heart rate, while observing the change in heart rate to prove the hypothesis ("Dependent Variable").
The above is also a perfect example of true experimental research design. As stated by the scientists publishing research on Explorable, using an experimental research design, "the researcher manipulates one variable," while either controlling or randomizing the dependent variable (Blackstad, "Experimental Research"). An experimental research design will have both a control group and a treatment group. The control group is not manipulated by the independent variable, while the treatment group is. Using a control group helps researchers determine if other factors unrelated to the independent variable are causing the changes (National Center for Technology Innovation, "Experimental Study Design").
When using descriptive research, researchers do not stimulate changes through manipulating variables. Instead, researchers simply observe behaviors to answer the "what is" question. After observation, researchers describe their findings, using "creative exploration" in order to "organize the findings" and assign to the findings explanations. One example of a useful descriptive study would be to find out if teachers "hold favorable attitudes toward using computers in schools?" (The Handbook of Research for Educational Communications and Technology, "41.1 What is Descriptive Research?").