Data definition, types and importance (Stats165)

Introduction 

Data refers to the raw facts, figures, or information collected for the purpose of analysis and decision-making. It serves as the raw material for any statistical investigation or analysis.

Depending on the source and method of collection, data can be classified into Primary Data and Secondary Data.

Data is a plural noun (the singular form is datum) 

Primary Data

Definition:

Primary data are first-hand information collected directly from respondents or original sources for a specific purpose. The data have not been previously collected or processed by anyone else.

Sources of Primary Data 

1. Census: e.g. Population census.

2. Sample Surveys: e.g. Social surveys, Industrial surveys, Medical surveys, Business surveys, and Educational surveys.

A survey

Methods of Collecting Primary Data 

• Observation
• Interviews 
• Questionnaires
• Experiments
• Focus group discussions

An interviewee 

Advantages of Primary Data

1. Accuracy: It provides the exact and specific information required for the study.

2. Reliability: Since the data are collected directly by the researcher, errors and misunderstandings are minimized. The process can be controlled and monitored.

3. Detail: Primary data often contain detailed and in-depth information relevant to the study.

Disadvantages of Primary Data

1. High Cost: Collecting primary data is usually expensive because it involves fieldwork, materials, and personnel.

2. Time-Consuming: It takes a long time to design instruments, collect responses, and process the data.

3. Non-Response Issues: Some respondents may fail to provide answers or may give incomplete information, which can affect the accuracy of results.

Secondary Data

Definition:

Secondary data refer to information that has already been collected, compiled, and possibly analyzed by someone else for a purpose other than the current research. Researchers use such data when it suits their study objectives.

Examples: Published statistical reports, journals, government records, and organizational databases.

Sources of Secondary Data

1. Publications: e.g. Statistical Abstracts, Bulletins, Annual Reports of WHO, ECOWAS, and the National Bureau of Statistics.

2. Research Organisations: e.g. Institute of Agricultural Research (IAR), Nigerian Institute of Social and Economic Research (NISER).

3. Tertiary Institutions: e.g. Universities and Polytechnics.

4. Media Organisations: e.g. Newspapers, Television, Radio.

5. Administrative Records: e.g. Government ministries, agencies, and company records.

Newspapers 

Advantages of Secondary Data

1. Time-Saving: The information is readily available and can be quickly gathered.

2. Cost-Effective: It is less expensive compared to collecting primary data.

3. Convenience: Data can be accessed from published or digital sources without direct fieldwork.

Disadvantages of Secondary Data 

1. Possible Inaccuracy: The data may not be reliable or may be outdated.

2. Irrelevance: The data might not perfectly suit the researcher’s current needs.

3. Lack of Control: The researcher has no control over how the data were originally collected or processed.

Conclusion 

In summary, data form the foundation of all statistical investigations and analyses. The distinction between primary and secondary data lies mainly in their sources and methods of collection. Primary data are original, specific, and reliable but often costly and time-consuming to obtain, while secondary data are readily available and economical, though they may lack precision or relevance to a specific study.

A good researcher should, therefore, choose the type of data that best suits the purpose, scope, and resources of the investigation to ensure valid, accurate, and meaningful results.

References 

U24PS Stats 165 note

Stat 165 key points by Rahmon Abass Adewale