Quantitative research, also called "empirical research," is research based on traditional scientific methods which generate numerical data and seek to establish causal relationships between two or more variables, using statistical methods to test the strength and significance of the relationships. Observations in quantitative research are measured in numbers.
Quantitative research starts with a testable hypothesis. One of the goals of quantitative research design is others can repeat the findings of the study. Some examples of quantitative research methods include close-ended interviews, surveys, clinical trials, and lab experiments.
Adapted from Finding Quantitative or Qualitative Nursing Research Articles (Simmons University)
Four main types of quantitative research design:
Descriptive Design - Seeks to describe the current status of a variable or phenomenon. The researcher develops a hypothesis after the data is collected. Data collection is mostly observational.
Correlational Design - Explores the relationship between variables using statistical analyses. The researcher does not look for cause and effect. Data collection is mostly observational.
Quasi-Experimental Design - Seeks to establish a cause-effect relationship between two or more variables. The researcher does not assign groups or manipulate the independent variable. Control groups are identified and exposed to the variable. Results are compared with results from groups not exposed to the variable.
Experimental Design - Uses the scientific method to establish cause-effect relationship among a group of variables in a research study. Researchers make an effort to control all variables except the one being manipulated (the independent variable). The effects of the independent variable on the dependent variable are collected and analyzed for a relationship.
Adapted from Quantitative Approaches - Center for Innovation in Research and Teaching
Qualitative research is research that seeks to provide understanding of human experience, perceptions, motivations, intentions, and behaviors based on description and observation, utilizing a naturalistic interpretative approach to a subject and its contextual setting. Observations in qualitative research are described in words.
Qualitative research starts with a situation the researcher can observe. One of the goals of qualitative research design is that participants are comfortable with the researcher and can be honest and forthcoming, allowing the researcher to make robust observations. Some examples of qualitative research methods include open-ended interviews, focus groups, and participant observation.
Adapted from Finding Quantitative or Qualitative Nursing Research Articles (Simmons University)
The following are the most common types of qualitative research methods:
Case Study - Describes in-depth the experience of one person, family, group, community, or institution. Data is collected through direct observation and interaction with the subject.
Ethnography - Describes a culture's characteristics. The researcher identifies the culture, variables, and review literature, then collects data through immersion into the culture, informants, direct observation, and interaction with subjects.
Grounded Theory - The purpose of this research is theory development. Grounded theory is used in discovering what problems exist in a social scene and how persons handle them. It involves formulation, testing, and redevelopment of propositions until a theory is developed. Data is collected through interview, observation, record review, or a combination.
Historical Research - Used to describe and examine events of the past to understand the present and anticipate potential future effects. An idea is formulated after reading related literature, followed by the development of a research question and an inventory of sources. The researcher clarifies the validity and reliability of data from primary sources, then develops a research outline and collects data.
Phenomenology - Describes experiences as they are lived. The researcher examines the uniqueness of individuals' lived situations and develops research questions from these observations. There is no clearly defined method of data collection to avoid limiting the creativity of the researcher.
Adapted from Qualitative Research Designs