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Public Health Research Guide: Primary & Secondary Data Definitions

Primary & Secondary Data Definitions

Primary Data: Data that has been generated by the researcher himself/herself, surveys, interviews, experiments, specially designed for understanding and solving the research problem at hand.

Secondary Data: Using existing data generated by large government Institutions, healthcare facilities etc. as part of organizational record keeping. The data is then extracted from more varied datafiles. 

Supplementary Data: A few years ago the Obama Administration judged that any research that is done using Federal Public funds should be available for free to the public. Moreover Data Management Plans should be in place to store and preserve the data for almost eternity. These data sets are published as Supplementary Materials in the journal lliterature, and data sets can downloaded and manipulated for research. 

NOTE: Even though the research is Primary source, the supplemental files downloaded by others becomes Secondary Source.


 Pros and Cons for each. 

Comparison Chart

Meaning Primary data refers to the first hand data gathered by the researcher himself. Secondary data means data collected by someone else earlier.
Data Real time data Past data
Process Very involved Quick and easy
Source Surveys, observations, experiments, questionnaire, personal interview, etc. Government publications, websites, books, journal articles, internal records etc.
Cost effectiveness Expensive Economical
Collection time Long Short
Specific Always specific to the researcher's needs. May or may not be specific to the researcher's need.
Available in Crude form Refined form
Accuracy and Reliability More Relatively less

Quantitative & Qualitative Research Methods

Quantitative Research Definition:  Data that can be measured, quantified. Basically Descriptive Statistics.

Read: Introduction to Quantitative Methods

Qualitative Research Definition: Data collected that is not numerical, hence cannot be quantified. It measures other characteristics through interviews, observation and focused groups among a few methods. It can also be termed as  "Categorical Statistics". 

Read: Qualitative methods in public health

Mixed methods research. When quantitative and qualitative research methods are used.

Qualitative Research Methods:

Method Overall Purpose Advantages Challenges
  • Quickly and/or easily gets lots of  information from people in a non threatening way
  • can complete anonymously
  • inexpensive to administer
  • easy to compare and analyze
  • administer to many people
  • can get lots of data
  • many sample questionnaires already exist
  • might not get careful feedback
  • wording can bias client's responses
  • impersonal
  • may need sampling expert
  • doesn't get full story
  • Understand someone's impressions or experiences
  • Learn more about answers to questionnaires
  • get full range and depth of information
  • develops relationship with client
  • can be flexible with client
  • can take ime
  • can be hard to analyze and compare
  • can be costly
  • interviewer can bias client's responses
  • Gather firsthand information about people, events, or programs
  • view operations of a program as they are actually occurring
  • can adapt to events as they occur
  • can be difficult to interpret seen behaviors
  • can be complex to categorize observations
  • can influence behaviors of program participants
  • can be expensive
Focus Groups
  • Explore a topic in depth through group discussion
  • quickly and reliably get common impressions
  • can be efficient way to get much range and depth of information in short time
  • can convey key information about programs
  • can be hard to analyze responses
  • need good facilitator for safety and closure
  • difficult to schedule 6-8 people together
Case Studies
  • Understand an experience or conduct comprehensive examination through cross comparison of cases
  • depicts client's experience in program input, process and results
  • powerful means to portray program to outsiders
  • usually time consuming to collect, organize and describe
  • represents depth of information, rather than breadth



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