Q.Define secondary data.

Secondary data is pre-existing data collected earlier by someone else for another purpose, which the current investigator reuses rather than collecting fresh.

In statistics, data is broadly classified into two kinds based on how it is obtained:

• Primary data is collected first-hand by the investigator specifically for the purpose of the current study/investigation (e.g. through a survey, direct observation, or an experiment conducted by the investigator).
• Secondary data is data that already exists — it was originally collected by some other person, agency, or organisation, usually for a different purpose, and the present investigator simply extracts and uses it.

Common sources of secondary data include government publications and reports, records of business/trade organisations, research papers and journals, newspapers and magazines, and international/institutional publications.

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Primary data is original, first-hand data collected directly from its source by the investigator for the specific purpose of the current study.

In statistics, data is classified as either primary or secondary based on its source:

Primary data is data that is collected directly and originally by the investigator (a person, agency, or organisation) through direct observation, interviews, questionnaires, surveys or experiments, specifically for the purpose at hand. Since it is collected first-hand, it is generally more reliable and specific to the study's needs, though it can be more time-consuming and costly to gather.

Example: A researcher personally surveying 500 households about their monthly electricity consumption is collecting primary data.

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