By submitting questionnaire to students in the dorm room and determining which variables, when present, seemed to correlate with higher grades and were potential 'causal' factors in higher grades, the researchers could then call their endeavor an experimental study. (Note that in this experiment there would be no formal control group, instead seeing what clusters of variables were present in high-achieving students would be the focus). In general, the great advantage of experiments over other study designs is that, with an experimental design, you can more easily demonstrate cause-and-effect relationships. Doing a simple observational case study of students on a dorm hall would expose the researcher to many extraneous variables that could affect students' study habits all at once, and would make it difficult to compare his or her study with other surveys of factors that enhance student performance on tests.

However, constructing studies that meet the criteria for experiments is not always feasible. Sometimes, ethically, a researcher may wish to study the effects of certain variables, like that of long-term illegal drug use, which cannot support an experimental design. Following the lives and surveying vital physical data about volunteers who were drug users might be one way to accumulate important data. "Perhaps the simplest [non-experimental] design is the correlational design or quasi-experimental design. A study qualifies as correlational if the data lend themselves only to interpretations about the degree to which certain things tend to...

"To conduct this [non-experimental] study, a set of children are observed for a period of one month by a set of trained observers, who record the number of violent acts the child engages in (e.g., hitting another child)" (Non-experimental design, 2009, UNE). Unlike a controlled experiment, only a correlation can be determined, as it may be possible that students who are in households with unsupervised television habits have less parental support, are more exposed to real violence in the household, and the violence they see on television is not the cause of their violent outbursts. A way of translating this into an experimental design might be to show children a violent cartoon in one room, and then see if they mimicked the behaviors they saw when playing with toys afterwards, when compared with a similar group of children who did not watch a film, or who watched a non-violent film.
References

Independent variables (IV) & Dependent variables (DV). (2009). UNCP.

Retrieved January 9, 2010 at http://www.uncp.edu/home/collierw/ivdv.htm

Non-experimental design. (2009). University of New England.

http://www.une.edu.au/WebStat/unit_materials/c2_research_design/design_nonexperimental.htm

Rumsey, Deborah. (2007). Intermediate statistics for dummies. New York: For Dummies.