By Purpose:
* Exploratory Research: This aims to explore a little-understood issue or topic. It's often used to formulate hypotheses or develop research questions for future, more rigorous studies. Examples include pilot studies, case studies, and secondary data analysis.
* Descriptive Research: This describes the characteristics of a population or phenomenon. It aims to answer "what" questions, not "why" questions. Examples include surveys, observational studies, and case studies focusing on detailed description.
* Explanatory Research: This seeks to explain the relationships between variables. It aims to answer "why" questions and establish cause-and-effect relationships. Examples include experiments, quasi-experiments, and some types of longitudinal studies.
* Evaluative Research: This assesses the effectiveness of a program, policy, or intervention. It often involves measuring outcomes and comparing them to goals or expectations. Examples include program evaluations, impact assessments, and cost-benefit analyses.
By Approach:
* Qualitative Research: This focuses on in-depth understanding of experiences, perspectives, and meanings. Data is often collected through interviews, focus groups, observations, and text analysis. It emphasizes rich descriptions and interpretations.
* Quantitative Research: This focuses on numerical data and statistical analysis. Data is collected through surveys, experiments, and other methods that yield quantifiable results. It emphasizes objectivity and generalizability.
* Mixed Methods Research: This combines both qualitative and quantitative approaches to gain a more comprehensive understanding of a research problem. It leverages the strengths of both approaches.
By Methodology:
* Experimental Research: This involves manipulating one or more independent variables to observe their effect on a dependent variable. It aims to establish causality. Includes randomized controlled trials (RCTs) and lab experiments.
* Correlational Research: This examines the relationship between two or more variables without manipulating them. It cannot establish causality but can identify associations.
* Causal-Comparative Research (Ex Post Facto): This examines the relationship between an independent and dependent variable after the fact. It looks back to understand what might have caused an outcome. Unlike experimental research, the independent variable is not manipulated.
* Descriptive Research (as mentioned above): This involves systematically describing a population, situation, or phenomenon.
* Case Study Research: This involves an in-depth investigation of a single case or a small number of cases. Can be qualitative, quantitative, or mixed methods.
* Longitudinal Research: This involves collecting data over an extended period to study changes and trends.
By Source of Data:
* Primary Research: This involves collecting original data directly from sources. Examples include conducting surveys, interviews, experiments, etc.
* Secondary Research: This involves analyzing existing data that has been collected by others. Examples include using census data, government reports, published articles, etc.
These categories are not mutually exclusive; a single research project can incorporate elements from multiple types. The best type of research depends on the research question, resources, and ethical considerations.