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Types of Research Studies

If you’re new to research, you may not know there are five main types of research studies. The choice of study type mainly depends on the research question being asked.

  • Randomized Controlled Trial: Best choice to determine how effective a treatment or diagnostic test is. Research subjects are randomly assigned to one of two or more groups. For example, one group would receive a new drug, while the other group would receive a placebo or the conventional treatment. Study groups are ideally assigned in a double-blind manner, in which neither the participants nor the researchers know who is in which group. This is the best choice when trying to determine a cause and effect relationship. Blinded RCTs are considered the gold standard for clinical trials.
  • Cohort Study: A type of observational longitudinal study in which groups of individuals are compared with each other over a period of time. The design can be prospective or retrospective. This type of study is a good choice for determining how common a condition is and what factors contribute to it.
  • Case-control Study: An observational study that compares a group of individuals with a certain disease or medical condition with another group that does not have the disease or condition to determine risk factors for disease. The two groups are otherwise as similar as possible. These studies are generally retrospective.
  • Cross-sectional Study: An observational study that analyzes data from a population or representative group at a specific point in time. An example of this type of study is a survey. Cross-sectional studies can generally be performed quickly and inexpensively.
  • Qualitative Study: Qualitative research focuses on the patient’s or study subject’s personal experiences and opinions using interviews, questionnaires, or first-hand observation. These studies can be useful adjuncts to quantitative research.

How do I decide which type of research study I should use?

The choice of study type depends on the research question being asked. The type of study design used to answer a particular research question is determined by the nature of question, the goal of research, and the availability of resources.

How reliable are the different study types?

Since the design of a study can affect the validity of its results, it is important to understand the different types of study designs and their strengths and limitations.

Consider whether the research study type you picked will actually find the answers you’re looking for. For instance, you can’t use a survey to determine what is causing a particular disease.

In order to get reliable results, a study has to be carefully planned from the start. One thing that is especially important to consider is which type of study is best suited to the research question. A study protocol should be written and complete documentation of the study’s process should also be done. This is vital in order for other scientists to be able to reproduce and check the results afterwards.

Information from: [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. What types of studies are there? 2016 Jun 15 [Updated 2016 Sep 8]. Available from: