In research the term data refers to raw information that is collected during course of conducting a research, which is then analysed to draw conclusions about the research subject or question being researched or investigated.
The research data is classified in two broad categories, primary data and secondary data, according to the sources of the data. The primary data is collected by the researcher directly from field research. This data may be in the form of responses of people to questionnaires, or during interviews, direct observations of objects, activities and phenomenons in their natural form, or experiments conducted in field. The secondary data is the data that is available form research or other studies conducted prior to the current research. Such data is available typically from books, journals, research reports, statistical data, and other similar sources. The secondary data may have been created for research in the same subject as that of the current research or some different subjects. Typically the secondary data represents the analysed information produced by earlier research efforts, but it can also include the primary data collected during the course of earlier research.
Generally it is less expensive and faster to collect the secondary data. For this reason it is best to first collect and analyse the available primary data before getting down to collecting the primary data. IN comparison secondary data is mor expensive and time consuming. However, the secondary data is not likely to cover all the aspects of the subject and question under investigation. Therefore, most of useful research cannot be completed without collection and analysis of some primary data.