What types of research studies are there?

Author: SCIRE Community Team | Reviewer: Janice Eng | Published: 24 April 2017 | Updated: 23 February 2024

There are many different types of research study designs. Below, we briefly outline the most common study designs used in SCI research.

The research design determines a study’s quality of evidence.⁴

In health research, the study design that provides the strongest evidence (as a single study) is called a randomized controlled trial, or RCT. RCTs are the most rigorous type of experimental study and can be used to determine whether a treatment actually caused the result.

RCTs are research experiments that place participants into at least two groups by chance, like the flip of a coin. One group (the experimental group) is given the treatment being tested and the other group (the control group) is given a comparison treatment or placebo. The two groups are then compared at the end of the study to see if they had different results.

In controlled trials without randomization, there is also an experimental group and a control group that are compared at the end of the study. However, unlike in RCTs, participants in these studies are not randomly assigned to their groups.

Because the groups are not randomly assigned, they may have additional differences that make a true comparison impossible. This type of study design is used when researchers cannot randomly assign participants into different groups.

Pre-post studies are one of the most common types of study designs used in SCI research. In this type of study, a group of people is tested before receiving a treatment and then afterwards. The difference between the “before” and “after” tests is thought to show the effects of the treatment.

Pre-post studies are used because they are often more convenient, ethical, and appropriate in a variety of different situations. However, because this study design does not control many of the factors that could affect the results of the study, it can be difficult to determine if changes in the results are caused by those other factors or the treatment itself.

Observational research involves observing what happens to a group of people over time when the researcher cannot control which participants receive which treatments. This type of research is used to observe connections and relationships between different factors.

Cohort studies are a type of observational study that follows up on or looks back on what happened to two (or more) comparable groups over time. The groups differ by an important characteristic, such as a health condition, risk factor, or treatment. The outcomes of the two groups are then compared to see how they differ over time.

Rats are often used in animal studies.⁵

Laboratory studies involving animals are usually done in an early stage of research to determine safety and if a treatment has potential before a risky procedure is used on people. Like human studies, there are strict ethical guidelines for performing studies involving animals. It is important to note that many treatments that are effective in animal studies are not effective in humans, so animal studies are considered introductory research that cannot simply be applied to humans as is.

Case studies describe the results of a treatment in a single individual (or case). Case studies are often used to communicate information when larger studies have not been done, or when it is difficult to do larger studies, like when a condition or treatment is extremely rare. A disadvantage of case studies is that because it is only based on one person, we do not know if the study’s conclusions also apply to other people. A case series is a study that includes multiple case studies.

Systematic reviews and meta-analyses summarize the findings of the research studies to answer specific research questions.⁶

Systematic reviews and meta-analyses combine the findings from all the studies on a topic together. This includes doing a systematic search for all the studies that address that topic, assessing the quality of each study, and interpreting the combined findings of all the studies together. Sometimes, systematic reviews may pool the data from different studies together and then analyze this grouped data. This is called a meta-analysis.

Systematic reviews and meta-analyses are considered the strongest form of research evidence to help with decision-making. These studies give greater context to the research and can weigh the findings of different studies against each other. However, systematic reviews and meta-analyses are only as strong as the studies they are based on, so they can still have some types of error.

While the research methods listed above are most often used for making treatment decisions, qualitative research methods like interviews and focus groups provide other important knowledge. Qualitative research seeks to describe the qualities of something to develop a deeper understanding about it. For example, qualitative research may be used to describe the qualities of pain after SCI or the effect that it has on people’s daily lives.