What types of studies are there? (2023)

There are various types of scientific studies such as experiments and comparative analyses, observational studies, surveys, or interviews. The choice of study type will mainly depend on the research question being asked.

When making decisions, patients and doctors need reliable answers to a number of questions. Depending on the medical condition and patient's personal situation, the following questions may be asked:

  • What is the cause of the condition?

  • What is the natural course of the disease if left untreated?

  • What will change because of the treatment?

  • How many other people have the same condition?

  • How do other people cope with it?

Each of these questions can best be answered by a different type of study.

In order to get reliable results, a study has to be carefully planned right 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.

The main types of studies are randomized controlled trials (RCTs), cohort studies, case-control studies and qualitative studies.

Randomized controlled trials

If you want to know how effective a treatment or diagnostic test is, randomized trials provide the most reliable answers. Because the effect of the treatment is often compared with "no treatment" (or a different treatment), they can also show what happens if you opt to not have the treatment or diagnostic test.

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When planning this type of study, a research question is stipulated first. This involves deciding what exactly should be tested and in what group of people. In order to be able to reliably assess how effective the treatment is, the following things also need to be determined before the study is started:

For instance, a medication used to treat menopause symptoms needs to be tested on a different group of people than a flu medicine. And a study on treatment for a stuffy nose may be much shorter than a study on a drug taken to prevent strokes.

“Randomized” means divided into groups by chance. In RCTs participants are randomly assigned to one of two or more groups. Then one group receives the new drug A, for example, while the other group receives the conventional drug B or a placebo (dummy drug). Things like the appearance and taste of the drug and the placebo should be as similar as possible. Ideally, the assignment to the various groups is done "double blinded," meaning that neither the participants nor their doctors know who is in which group.

The assignment to groups has to be random in order to make sure that only the effects of the medications are compared, and no other factors influence the results. If doctors decided themselves which patients should receive which treatment, they might – for instance – give the more promising drug to patients who have better chances of recovery. This would distort the results. Random allocation ensures that differences between the results of the two groups at the end of the study are actually due to the treatment and not something else.

Randomized controlled trials provide the best results when trying to find out if there is a cause-and-effect relationship. RCTs can answer questions such as these:

  • Is the new drug A better than the standard treatment for medical condition X?

  • Does regular physical activity speed up recovery after a slipped disk when compared to passive waiting?

Cohort studies

A cohort is a group of people who are observed frequently over a period of many years – for instance, to determine how often a certain disease occurs. In a cohort study, two (or more) groups that are exposed to different things are compared with each other: For example, one group might smoke while the other doesn't. Or one group may be exposed to a hazardous substance at work, while the comparison group isn't. The researchers then observe how the health of the people in both groups develops over the course of several years, whether they become ill, and how many of them pass away. Cohort studies often include people who are healthy at the start of the study. Cohort studies can have a prospective (forward-looking) design or a retrospective (backward-looking) design. In a prospective study, the result that the researchers are interested in (such as a specific illness) has not yet occurred by the time the study starts. But the outcomes that they want to measure and other possible influential factors can be precisely defined beforehand. In a retrospective study, the result (the illness) has already occurred before the study starts, and the researchers look at the patient's history to find risk factors.

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Cohort studies are especially useful if you want to find out how common a medical condition is and which factors increase the risk of developing it. They can answer questions such as:

  • How does high blood pressure affect heart health?

  • Does smoking increase your risk of lung cancer?

For example, one famous long-term cohort study observed a group of 40,000 British doctors, many of whom smoked. It tracked how many doctors died over the years, and what they died of. The study showed that smoking caused a lot of deaths, and that people who smoked more were more likely to get ill and die.

Case-control studies

Case-control studies compare people who have a certain medical condition with people who do not have the medical condition, but who are otherwise as similar as possible, for example in terms of their sex and age. Then the two groups are interviewed, or their medical files are analyzed, to find anything that might be risk factors for the disease. So case-control studies are generally retrospective.

Case-control studies are one way to gain knowledge about rare diseases. They are also not as expensive or time-consuming as RCTs or cohort studies. But it is often difficult to tell which people are the most similar to each other and should therefore be compared with each other. Because the researchers usually ask about past events, they are dependent on the participants’ memories. But the people they interview might no longer remember whether they were, for instance, exposed to certain risk factors in the past.

Still, case-control studies can help to investigate the causes of a specific disease, and answer questions like these:

  • Do HPV infections increase the risk of cervical cancer?

  • Is the risk of sudden infant death syndrome (“cot death”) increased by parents smoking at home?

Cohort studies and case-control studies are types of "observational studies."

Cross-sectional studies

Many people will be familiar with this kind of study. The classic type of cross-sectional study is the survey: A representative group of people – usually a random sample – are interviewed or examined in order to find out their opinions or facts. Because this data is collected only once, cross-sectional studies are relatively quick and inexpensive. They can provide information on things like the prevalence of a particular disease (how common it is). But they can't tell us anything about the cause of a disease or what the best treatment might be.

Cross-sectional studies can answer questions such as these:

  • How tall are German men and women at age 20?

  • How many people have cancer screening?

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Qualitative studies

This type of study helps us understand, for instance, what it is like for people to live with a certain disease. Unlike other kinds of research, qualitative research does not rely on numbers and data. Instead, it is based on information collected by talking to people who have a particular medical condition and people close to them. Written documents and observations are used too. The information that is obtained is then analyzed and interpreted using a number of methods.

Qualitative studies can answer questions such as these:

How reliable are the different types of studies?

Each type of study has its advantages and disadvantages. It is always important to find out the following: Did the researchers select a study type that will actually allow them to find the answers they are looking for? You can’t use a survey to find out what is causing a particular disease, for instance.

It is really only possible to draw reliable conclusions about cause and effect by using randomized controlled trials. Other types of studies usually only allow us to establish correlations (relationships where it isn’t clear whether one thing is causing the other). For instance, data from a cohort study may show that people who eat more red meat develop bowel cancer more often than people who don't. This might suggest that eating red meat can increase your risk of getting bowel cancer. But people who eat a lot of red meat might also smoke more, drink more alcohol, or tend to be overweight. The influence of these and other possible risk factors can only be determined by comparing two equal-sized groups made up of randomly assigned participants.

(Video) Study Designs (Cross-sectional, Case-control, Cohort) | Statistics Tutorial | MarinStatsLectures

That is why randomized controlled trials are usually the only suitable way to find out how effective a treatment is. Systematic reviews, which summarize multiple RCTs, are even better. In order to be good-quality, though, all studies and systematic reviews need to be designed properly and eliminate as many potential sources of error as possible.

Sources

  • German Network for Evidence-based Medicine. Glossar: Qualitative Forschung.Berlin: DNEbM; 2011.

  • Greenhalgh T. Einführung in die Evidence-based Medicine: kritische Beurteilung klinischer Studien als Basis einer rationalen Medizin. Bern: Huber; 2003.

  • Institute for Quality and Efficiency in Health Care (IQWiG, Germany). General methods. Version 5.0. Cologne: IQWiG; 2017.

  • Klug SJ, Bender R, Blettner M, Lange S. Wichtige epidemiologische Studientypen. Dtsch Med Wochenschr 2007; 132:e45-e47. [PubMed: 17530597]

  • Schäfer T. Kritische Bewertung von Studien zur Ätiologie. In: Kunz R, Ollenschläger G, Raspe H, Jonitz G, Donner-Banzhoff N (eds.). Lehrbuch evidenzbasierte Medizin in Klinik und Praxis. Cologne: Deutscher Ärzte-Verlag; 2007.

  • IQWiG health information is written with the aim of helpingpeople understand the advantages and disadvantages of the main treatment options and healthcare services.

    Because IQWiG is a German institute, some of the information provided here is specific to theGerman health care system. The suitability of any of the described options in an individualcase can be determined by talking to a doctor. We do not offer individual consultations.

    (Video) What Are Observational And Experimental Studies In Statistics - Types Of Studies Explained

    Our information is based on the results of good-quality studies. It is written by ateam ofhealth care professionals, scientists and editors, and reviewed by external experts. You canfind a detailed description of how our health information is produced and updated inour methods.

FAQs

What types of studies are there? ›

The main types of studies are randomized controlled trials (RCTs), cohort studies, case-control studies and qualitative studies.

What are the 3 types of studies? ›

We can divide scientific studies on relationships into three main types: survey-type, observational and experimental.

What are the 3 types of observational study? ›

Three types of observational studies include cohort studies, case-control studies, and cross-sectional studies (Figure 1).

What are the 4 types of study design? ›

There are four main types of Quantitative research: Descriptive, Correlational, Causal-Comparative/Quasi-Experimental, and Experimental Research. attempts to establish cause- effect relationships among the variables. These types of design are very similar to true experiments, but with some key differences.

How many types of study methods are there? ›

There are 4 main types of learning styles: Visual, Auditory, Reading/Writing and Kinesthetic.

What are the two categories of studies? ›

There are two main categories of research methods: qualitative research methods and quantitative research methods. Quantitative research methods involve using numbers to measure data.

What are the primary studies? ›

Primary research or a primary study refers to a research article that is an author's original research that is almost always published in a peer-reviewed journal. A primary study reports on the details, methods and results of a research study.

What are types of primary studies? ›

Primary research is any type of research that you collect yourself. Examples include surveys, interviews, observations, and ethnographic research.

What are the three 3 methods of study designs? ›

Common types of qualitative design include case study, ethnography, and grounded theory designs.

What is an example of a cohort study? ›

Some examples of cohort studies are (1) Framingham Cohort study, (2) Swiss HIV Cohort study, and (3) The Danish Cohort study of psoriasis and depression. These studies may be prospective, retrospective, or a combination of both of these types.

What type of study is an experimental study? ›

Experimental studies are ones where researchers introduce an intervention and study the effects. Experimental studies are usually randomized, meaning the subjects are grouped by chance. Randomized controlled trial (RCT): Eligible people are randomly assigned to one of two or more groups.

What are the 10 types of research? ›

Types of research
  • Fundamental research. Fundamental, also known as basic or theoretical, research is designed to help researchers better understand certain phenomena in the world. ...
  • Applied research. ...
  • Action research. ...
  • Causal research. ...
  • Classification research. ...
  • Comparative research. ...
  • Cross-sectional research. ...
  • Deductive research.
Jan 13, 2021

What are the 7 types of research design? ›

Introduction
  • General Structure and Writing Style.
  • Action Research Design.
  • Case Study Design.
  • Causal Design.
  • Cohort Design.
  • Cross-Sectional Design.
  • Descriptive Design.
  • Experimental Design.
Dec 8, 2022

What are the 7 kinds of quantitative research? ›

7 Types of Quantitative Research
  • Causal Comparative Research. Causal comparative research is also commonly referred to as quasi experimental research. ...
  • Cross Sectional Survey. ...
  • Sampling Methods. ...
  • Commercial Information. ...
  • Educational Institutes. ...
  • Government Resources. ...
  • Internet Data.
Mar 16, 2021

How do you identify a study type? ›

Summary:
  1. Step 1: Determine what the exposure and outcome are in the given question.
  2. Step 2: Determine if it is an observational or experimental study by reading the question carefully.
  3. Step 3: Ascertain if key words give away the design (read the sub-questions carefully):
Aug 17, 2017

What is the most popular study? ›

An inspection of those areas for the class of 2022 high school graduates shows the 10 most popular areas of interest to be:
  • Biology, 11.80% of prospective students.
  • Business and Management, 10.93%
  • Nursing, 8.07%
  • Engineering, 7.12%
  • Psychology, 6.67%
  • Computer Science, 4.65%
  • Education, 4.49%
  • Criminal Justice, 4.01%
Feb 16, 2022

What are the 8 study skills? ›

Active listening, reading comprehension, note taking, stress management, time management, testing taking, and memorization are only a few of the topics addressed in our study skills guides for students.

What study methods are most effective? ›

Shorter, intensive study times are more effective than drawn out studying. In fact, one of the most impactful study strategies is distributing studying over multiple sessions (Newport, 2007). Intensive study sessions can last 30 or 45-minute sessions and include active studying strategies.

What are the best ways to study? ›

Part 5 – How to Study More Efficiently
  1. Take Regular Breaks. Study sessions will be more productive if you allow yourself to take planned breaks. ...
  2. Take Notes in Class. ...
  3. Exercise First. ...
  4. Review and Revise Your Notes at Home. ...
  5. Start with Your Toughest Assignments. ...
  6. Focus on Key Vocabulary. ...
  7. Join a Study Group.
Nov 6, 2022

How many levels of study are there? ›

Education levels

All courses and programmes at universities and university colleges are divided into three levels: bachelor's (first cycle) master's (second cycle) doctoral (third cycle)

What are the groups in a study? ›

An experimental group, also known as a treatment group, receives the treatment whose effect researchers wish to study, whereas a control group does not. They should be identical in all other ways. Do experiments always need a control group?

What are the 5 main types of primary research? ›

Examples of primary research are:
  • Interviews (telephone or face-to-face)
  • Surveys (online or mail)
  • Questionnaires (online or mail)
  • Focus groups.
  • Visits to competitors' locations.

What is an example of secondary research? ›

Common examples of secondary research include textbooks, encyclopedias, news articles, review articles, and meta analyses. When conducting secondary research, authors may draw data from published academic papers, government documents, statistical databases, and historical records.

What is a primary qualitative study? ›

Primary Qualitative Methods

Surveys - a survey gathers information via a questionnaire. It may involve quantitative as well as qualitative data. Interviews - involves asking subjects questions, generally intending open-ended responses.

What is the easiest career to study? ›

The 16 Easiest College Majors – 2023 Rankings
  • Psychology.
  • Criminal Justice.
  • English.
  • Education.
  • Religious Studies.
  • Social Work.
  • Sociology.
  • Communications.
Nov 1, 2022

What are the six main research methods? ›

In conducting research, sociologists choose between six research methods: (1) survey, (2) participant observation, (3), secondary analysis, (4) documents, (5) unobtrusive measures, and (6) experiments.

What are the major types of research *? ›

There are three main research methodologies:
  • Observational research (qualitative)
  • Correlational research (non-experimental quantitative)
  • Experimental research (quantitative)
Jan 12, 2022

What are the 7 qualitative research? ›

Grounded theory, ethnographic, narrative research, historical, case studies, and phenomenology are several types of qualitative research designs. The proceeding paragraphs give a brief over view several of these qualitative methods.

What are the 11 research process? ›

"11 Steps" basically consists of 11 stages that complement each other as a method of discussion. This phased classification is as follows: Manifestation, Description, Prediction, Investigation, Determination, Diagnosis, Verification, Treatment, Reinforcement, Progress, and Tracking.

What are the 8 elements of research? ›

Research elements
  • 1) THE RESEARCH QUESTION: The best research question should specify just one measurable result, as well as all the conditions and important variables. ...
  • 2) HYPOTHESIS: ...
  • 3) RANDOMIZATION: ...
  • 4) POPULATION: ...
  • 5) SAMPLE: ...
  • 6) SAMPLING: ...
  • 7) MANOEUVRE: ...
  • 8) RESULT OR OUTCOME:

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