In statistics, primary data and secondary data refer to the sources from which data is obtained.

Primary data is original data that is collected directly from the source, usually through methods such as surveys, experiments, or observations. This data is collected by the researcher for the specific purpose of the study and has not been previously published or used. Examples of sources of primary data include:

Surveys: questionnaires or interviews administered to individuals or groups
Experiments: controlled studies in which variables are manipulated and outcomes are measured
Observations: systematic observation of individuals or phenomena in natural settings

Secondary data, on the other hand, is data that has been previously collected and published by another person or organization. This data is used for a different purpose than the original collection, and the researcher does not have control over the data-collection methods. Examples of sources of secondary data include:

Government reports and statistics
News articles and publications
Historical records and archives
Online databases and platforms
Social media data

In summary, primary data is collected directly by the researcher for a specific study, while secondary data is collected by someone else and used for a different purpose.