Scientists of every specialty, from sociology to astronomy, employ various research methods for data collection. Data are placed into two categories -- primary and secondary -- depending on who gathered the research.

Primary Data

If you survey your classmates and ask them to describe what they ate for breakfast, you are collecting primary data. Research trials and surveys both generate primary, or original, data. This information can be qualitative -- including feelings or opinions expressed in response to questions -- or quantitative or mathematical, such as the height or weight of the students.

Secondary Data

Information that has been collected by someone else but is being used for your research is secondary data. The census can be an example of secondary data -- it is the result of questions asked over many years. The advantage of secondary data is that this information is inexpensive and easy to access, and may allow for more extensive research than one scientist or a team could gather on their own.