There are many ways of classifying data.
A common classification is based upon who collected the data.
Primary data: Data collected by the investigator himself/ herself for a specific purpose.
Examples: Data collected by a student for his/her thesis or research project.
(In movies) The hero is directly told by the heroine that he is her “ideal man”.
Secondary data: Data collected by someone else for some other purpose (but being utilized by the investigator for another purpose).
Examples: Census data being used to analyze the impact of education on career choice and earning.
(In movies) The hero reads a fictional account of the heroine’s “ideal man” (written for a course in English composition) that seems to describe him accurately. He seeks confirmation from his friends, concluding that he is her “ideal man”. (He never asks her directly, but assumes the “facts” are correct).
Some Advantages of using Primary data:
- The investigator collects data specific to the problem under study.
- There is no doubt about the quality of the data collected (for the investigator).
- If required, it may be possible to obtain additional data during the study period.
Some Disadvantages of using Primary data (for reluctant/ uninterested investigators):
- The investigator has to contend with all the hassles of data collection-
- deciding why, what, how, when to collect
- getting the data collected (personally or through others)
- getting funding and dealing with funding agencies
- ethical considerations (consent, permissions, etc.)
2. Ensuring the data collected is of a high standard-
- all desired data is obtained accurately, and in the format it is required in
- there is no fake/ cooked up data
- unnecessary/ useless data has not been included
3. Cost of obtaining the data is often the major expense in studies
Some Advantages of using Secondary data:
- The data’s already there- no hassles of data collection
- It is less expensive
- The investigator is not personally responsible for the quality of data (“I didn’t do it”)
Some disadvantages of using Secondary data:
- The investigator cannot decide what is collected (if specific data about something is required, for instance).
- One can only hope that the data is of good quality
- Obtaining additional data (or even clarification) about something is not possible (most often)
Link to revised article on primary and secondary data: