Exploratory study is the preliminary study of an unfamiliar problem about which the researcher is not quite familiar. It is carried out to gain a degree of familiarity required to intelligently generate new ideas or to formulate a research problem. The exploratory research needs to be carried out quickly and without too much expense. Therefor such research relies primarily on review of available literature and secondary sources of data.
Descriptive study is a fact finding investigation carried out with the objective of ascertaining and describing describing some aspect of the subject or area under study as it exists at present. This kind of study concentrates on collecting detailed field data of things as they exist, with limited stress on analysis. The analysis in this type of studies consist mostly in ordering and classifying variable rather than finding relationships between different variables.
Causal studiesis, also called analytical research, is concerned with understanding the relationships that exists between different variables relating to a field or subject under study. It generally involves testing of hypothesis. It specifies and interprets relationships by analyzing facts available or collected for the research. Effectively research of this type requires formulation of a good hypothesis and designing the complete research around testing oh this hypothesis. Research of this type relies considerably on collection of data and their analysis.