Glossary of research terms

Please find below explanations for the most common terms used in the organisation and delivery of research studies. If there is another word on the site that you'd like us to consider adding to the glossary, let us know by emailing

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A brief summary of a research study and its results. It should tell you why the study is taking place, how the researchers will go about it and what they hope to find.

Advisory group

Many research projects have an advisory group (or steering group) that helps develop, support, advise and monitor the project. The group often includes people who use services, carers, researchers and other health and social care professionals.


Where no one, including the researcher, knows the identities of the people taking part in the research.



A measurement carried out before an experimental treatment to allow for a comparison and to see if the treatment tested has caused any changes.


A loss of balance and accuracy in research. Bias means that the research findings will not be representative of, or generalisable to, a wider population.

Blind study   

This is a study where the people taking part don’t know which treatment they are getting.



Having capacity in the context of mental health, means you can make your own decisions. Someone lacking capacity, because of an illness or disability such as a mental health problem, dementia or a learning disability, would be unable to understand, retain and weigh up information given to them and then communicate their decision.


A member of a family, friend or paid helper who regularly looks after a family member, partner or friend because of their illness, frailty, disability, mental health condition or addiction.  

Chief Investigator

This is the person who has overall responsibility for the design, organisation, delivery, and reporting of a study.


Asking members of the public for their views about research, and then using those views to inform decision-making. Having a better understanding of people’s views should lead to better decisions.

Consent / Informed consent

When you give permission, knowing you have all the information you need and are aware of the benefits and consequences of taking part.


Also sometimes called novel coronavirus. The acronym stands for Corona Virus Disease 2019. 



Communicating the findings of a research study to a wide range of people who might find it useful.

Double-blind study

This is where neither the researcher nor the people taking part know who is receiving which treatment.


Eligibility criteria

set of requirements or characteristics that people must have in order to join a research study. These include inclusion criteria and exclusion criteria. For example, a study might only accept participants who are above or below certain ages.


Moral principles that guide researchers. Research ethics are a set of principals that are designed to govern behaviour to protect the safety, dignity, rights and well-being of the people taking part.

Ethics committee / Research Ethics Committee (REC)

Research ethics committees are a set of people who review research applications and give an opinion about whether the research is ethical or not. They ensure that research ethics are upheld (see above). 

Exclusion criteria 

People who have these specific characteristics cannot take part in a particular study. This may be for different reasons, for example if a person is already taking a medication that may make it harder for a researcher to see if the treatment being trialled is effective.


This is a summary of how well the study did and whether it met its aims.

Evidence base 

A collection of all the research data currently available about a topic, such as how well a treatment or service works. This evidence is used by health and social care professionals to make decisions about the services, care or treatment they provide.


Focus groups 

Small, roundtable discussion groups responsible for looking at and talking about specific topics or problems.


Health Research Authority (HRA)

The HRA is a part of the Department of Health and Social Care that provides and ensures that standards for health research are met in England and Wales.

Healthy Volunteer

Someone with no known significant health problems who participates in research to test a new drug, device or intervention. Read more about who can take part in health research.


Interventional study

These studies are where volunteers who’ve signed up are given a new treatment or medicine. Researchers then study the effects of that treatment on the volunteers. The treatment is known as an intervention and could be a drug, a counselling service, x-ray, some information or training.

Inclusion criteria 

A set of characteristics that describe people who may be able to take part in a study. The opposite of exclusion criteria.


Lasting power of attorney (LPA)

A legal document that lets you appoint one or more people to help you make decisions or to make decisions on your behalf without any time limits. This gives you more control over what happens to you if you have an accident or an illness and cannot make your own decisions. See also power of attorney.

Lay summary

This is a brief summary of a research study or a research application that has been written for members of the public, rather than for researchers or professionals.


Mental Capacity

In the context of mental health, having capacity means you are able to understand, retain and weigh up information given to you and can then communicate your decision.


The approach of how the research study will and should proceed.


National Institute of Clinical Excellence (NICE)

NICE is a part of the Department of Health and Social Care and is responsible for overseeing the use of new and existing medicines, treatments and procedures. They also publish guidance.


Observational studies

Are where the study team observe the effects and behaviours on a wider group of people and then use this information to make a decision. A good example of this would be a survey or questionnaire.


This is a unique number given to researchers.

Outcome measures 

Measurements of the effects of a treatment or service. They might include physical measurements, (for example, measuring blood pressure), or psychological measurements (for example, measuring people’s sense of well-being).



Someone who takes part in a study.

Peer review 

The process in which the researcher submits a write up of their work to other research experts in the field for critical evaluation.

Phases of a trial

There are 3 main phases of clinical trials:

  • Phase 1 assesses how safe the drug or device is.
  • Phase 2 will test how effective the drug or device is.
  • Phase 3 involves randomised and blind testing in several hundred to several thousand patients.


A fake or dummy treatment that is designed to be harmless and to have no effect. It allows researchers to test for the ‘placebo effect’. The placebo effect is a psychological response where people feel better because they have received a treatment, and not because the treatment has a specific effect on their condition.

By comparing people’s responses to the placebo and to the treatment being tested, researchers can tell whether the treatment is having any real benefit.

Power of attorney

In order to allow someone to act on your behalf for a financial or medical decision, you'll need to give them ‘Power of Attorney’.  There's a legal document that allows you to do this. You can only set one up while you still have the ability to weigh up information and make decisions for yourself.  See also Lasting power of attorney.

Principal Investigator

The person responsible for the design and conduct of a research project.


This is the plan for a piece of research. It usually includes:

  • what question the research is asking and its importance / relevance
  • the background including what other research has been done before
  • how many people will be involved
  • who can take part
  • how the research will be carried out
  • what will happen to the results and how they will be publicised

Usually, it cannot be changed without going back to a research ethics committee or funder for approval.

Randomised control

This is a type of scientific experiment which is used to reduce bias when testing a new treatment. Participants are randomly allocated to 1 of 2 groups. One group receives the new treatment, the other group will receive standard treatment as the control. 



This may refer to a small group of people that will be used to represent the larger population. They need to reflect the larger group. It can also be referring to a tissue sample or blood sample.


This is the individual or organisation that takes the responsibility to set up, manage or fund the study. They don’t actually carry out the research.


Trial ID 

Is a unique number given to every research study.

Trial status

When you look at a study on this site, you will see a trial status. It will be one of the following:

  • Recruiting: this study is currently seeking volunteers to take part in the study and enrolling those who are interested and suitable. This site defaults to show all studies presently recruiting.
  • Not recruiting: the study is not yet enrolling people, but it might be underway.
  • Completed: the study has ended and participants are no longer being examined or treated.
  • Stopped: this suggests that recruiting or enrolling participants has ended early.


In research, this is likely to mean human material, like blood, biopsies, or urine.



Any characteristic or trait that can differ from one person to another (for example, race, gender or academic major) or for one person over time (for example, age or political beliefs).