The types of original research include.
Case study -- A detailed analysis of a person or group, especially as a model of medical, psychiatric, psychological, or social phenomena.
Controlled experiment -- An experiment that isolates the effect of one variable on a system by holding constant all variables but the one under observation. (Only this type of research can identify causation.)
Correlational study -- A study in which a researcher investigates the relationships between different variables. (In other words, if x is changed, how does y change, or does it?)
Naturalistic observation -- a research technique in which a subject is observed in its natural habitat without any manipulation by the observer.
Survey -- A data collection tool to gather self-reported factual information or opinion from respondents.