Study design

Study design is a key component in research methodology that defines the structure, strategy, experimental design, and method to be used in a research study. The design of a study defines the study type (descriptive, correlational, semi-experimental, experimental, review, meta-analytic) and sub-type (e.g., descriptive-longitudinal case study), research problem, hypotheses, independent and dependent variables, experimental design, and, if applicable, data collection methods and a statistical analysis plan. Study design is a framework that combines different components of research in a coherent and logical way, thereby ensuring that the research problem is efficiently handled.

Types of Study Design

There are several types of study designs, each with its own strengths and weaknesses.

• Descriptive studies: These are observational studies which describe the characteristics of a population or phenomenon being studied. They can answer questions about "what" or "who" and their outcome measures are often times based on prevalence and incidence.

• Analytical studies: These are designed to test hypotheses. They are often times divided into observational (i.e., cohort studies, case-control studies, and cross-sectional studies) and experimental (i.e., randomized controlled trials).

• Experimental studies: These are studies in which the researcher manipulates some of the conditions and controls others. They can be either a randomized controlled trial or a quasi-experiment.

• Observational studies: These are studies in which the researcher observes the effect of a risk factor, diagnostic test, treatment or other intervention without trying to change who is or isn't exposed to it. Cohort studies and case-control studies are examples of observational studies.

• Longitudinal studies: These involve repeated observations of the same variables over long periods of time.

• Cross-sectional studies: These are observational in nature and are known as descriptive research, not causal or relational, meaning that you can't use them to determine causes of phenomena.

Choosing a Study Design

The choice of study design depends on the research question. For example, if the research question is about testing whether a specific intervention influences an outcome, then a randomized controlled trial would be the best design. If the research question is about what factors influence an outcome, then a cohort study or case-control study would be the best design.

See Also

• Research design
• Scientific method
• Statistical hypothesis testing
• Clinical study design

References

Study design Resources
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