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Systematic Reviews in the Health Sciences: Types of Research within Qualitative and Quantitative

This guide will introduce you to the Systematic Review process.

Aspects of Quantitative (Empirical Research)

What is the basic methodology for a quantitative research design?

The overall structure for a quantitative design is based in the scientific method.  It uses deductive reasoning, where the researcher forms an hypothesis, collects data in an investigation of the problem, and then uses the data from the investigation, after analysis is made and conclusions are shared, to prove the hypotheses not false or false.  The basic procedure of a quantitative design is:

  1. Make your observations about something that is unknown, unexplained, or new.  Investigate current theory surrounding your problem or issue. 
  1. Hypothesize an explanation for those observations.
  1. Make a prediction of outcomes based on your hypotheses. Formulate a plan to test your prediction.
  1. Collect and process your data. If your prediction was correct, go to step 5. If not, the hypothesis has been proven false. Return to step 2 to form a new hypothesis based on your new knowledge.

  2. Verify your findings.  Make your final conclusions.  Present your findings in an appropriate form for your audience.

Types of Quantatitive Research

1. Descriptive researchseeks to describe the current status of an identified variable. These research projects are designed to provide systematic information about a phenomenon.  The researcher does not usually begin with an hypothesis, but is likely to develop one after collecting data.  The analysis and synthesis of the data provide the test of the hypothesis.  Systematic collection of information requires careful selection of the units studied and careful measurement of each variable.


2. Correlational researchattempts to determine the extent of a relationship between two or more variables using statistical data.  In this type of design, relationships between and among a number of facts are sought and interpreted. This type of research will recognize trends and patterns in data, but it does not go so far in its analysis to prove causes for these observed patterns. Cause and effect is not the basis of this type of observational research. The data, relationships, and distributions of variables are studied only. Variables are not manipulated; they are only identified and are studied as they occur in a natural setting. 

*Sometimes correlational research is considered a type of descriptive research, and not as its own type of research, as no variables are manipulated in the study


3. Causal-comparative/quasi-experimental researchattempts to establish cause-effect relationships among the variables.  These types of design are very similar to true experiments, but with some key differences.  An independent variable is identified but not manipulated by the experimenter, and effects of the independent variable on the dependent variable are measured. The researcher does not randomly assign groups and must use ones that are naturally formed or pre-existing groups. Identified control groups exposed to the treatment variable are studied and compared to groups who are not. 

When analyses and conclusions are made, determining causes must be done carefully, as other variables, both known and unknown, could still affect the outcome.  


4. Experimental researchoften called true experimentation, uses the scientific method to establish the cause-effect relationship among a group of variables that make up a study.  The true experiment is often thought of as a laboratory study, but this is not always the case; a laboratory setting has nothing to do with it.  A true experiment is any study where an effort is made to identify and impose control over all other variables except one.  An independent variable is manipulated to determine the effects on the dependent variables.  Subjects are randomly assigned to experimental treatments rather than identified in naturally occurring groups.


Aspects of Qualitative Design

Qualitative methodology is inductive in its reasoning.  The researcher selects a general topic and then begins collecting information to assist in the formation of an hypothesis.  The data collected during the investigation creates the hypothesis for the researcher in this research design model. 

What is the basic methodology for a QUALITATIVE research design?

1. Identify a general research question.

2. Choose main methods, sites, and subjects for research. Determine methods of documentation of data and access to subjects.

3. Decide what you will collect data on: questions, behaviors to observe, issues to look for in documents (interview/observation guide), how much (# of questions, # of interviews/observations, etc.).

4. Clarify your role as researcher.  Determine whether you will be obtrusive or unobtrusive, objective or involved.

5.  Study the ethical implications of the study.  Consider issues of confidentiality and sensitivity.

6.  Begin to collect data and continue until you begin to see the same, repeated information, and stop finding new information.

7.  Interpret data.  Look for concepts and theories in what has been collected so far.

8.  Revise the research question if necessary and begin to form hypotheses.

9.  Collect further data to address revisions.  Repeat Steps 6 and 7.

10.  Verify your data.  Complete conceptual and theoretical work to make your findings.  Present your findings in an appropriate form to your audience.

Types of Qualitative Research


What are the main types of qualitative approaches to research?

While there are many different investigations that can be done, a study with a qualitative approach generally can be described with the characteristics of one of the following three types:

Historical research describes past events, problems, issues and facts.  Data are gathered from written or oral descriptions of past events, artifacts, etc.  It describes “what was” in an attempt to recreate the past.  It is different from a report in that it involves interpretation of events and its influence on the present.  It answers the question: “What was the situation?” 

Examples of Historical Research:

  • A study of the factors leading to the historical development and growth of cooperative learning
  • A study of the effects of the historical decisions of the United States Supreme Court on American prisons
  • A study of the evolution of print journalism in the United States through a study of collections of newspapers
  • A study of the historical trends in public laws by looking recorded at a local courthouse

Ethnographic research develops in-depth analytical descriptions of current systems, processes, and phenomena and/or understandings of the shared beliefs and practices of a particular group or culture.  This type of design collects extensive narrative data (non-numerical data) based on many variables over an extended period of time in a natural setting within a specific context. The background, development, current conditions, and environmental interaction of one or more individuals, groups, communities, businesses or institutions is observed, recorded, and analyzed for patterns in relation to internal and external influences.  It is a complete description of present phenomena.

One specific form of ethnographic research is called a case study.  It is a detailed examination of a single group, individual, situation, or site. 

A meta-analysis is another specific form.  It is a statistical method which accumulates experimental and correlational results across independent studies.  It is an analysis of analyses.

Examples of Ethnographic Research:

  • A case study of parental involvement at a specific magnet school
  • A multi-case study of children of drug addicts who excel despite early childhoods in poor environments
  • The study of the nature of problems teachers encounter when they begin to use a constructivist approach to instruction after having taught using a very traditional approach for ten years
  • A psychological case study with extensive notes based on observations of and interviews with immigrant workers
  • A study of primate behavior in the wild measuring the amount of time an animal engaged in a specific behavior

Narrative research focuses on studying a single person and gathering data through the collection of stories that are used to construct a narrative about the individual’s experience and the meanings he/she attributes to them.

Examples of Narrative Research:

  • A study of the experiences of an autistic student who has moved from a self-contained program to an inclusion setting
  • A study of the experiences of a high school track star who has been moved on to a championship-winning university track team

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