The NICE glossary provides brief definitions and explanations of terms used on the website. The terms describe how NICE works and how its guidance is produced.

Our glossary excludes specific clinical and medical terms. If you cannot find the term you are looking for, please email us so that we can consider adding it to the glossary.

Some definitions and examples are based on those in the HTAi consumer and patient glossary, with thanks to Health Technology Assessment International.

For terms used in social care, the Care and Support Jargon Buster from Think Local Act Personal is a useful guide to the most commonly used social care words and phrases, and what they mean.

  • Random allocation

    See Randomisation

  • Randomisation

    Assigning people in a research study to different groups without taking any similarities or differences between them into account. For example, it could involve using a random numbers table or a computer-generated random sequence. It means that each individual (or each group in the case of cluster randomisation) has the same chance of having each intervention.

  • Randomised controlled trial

    A study in which a number of similar people are randomly assigned to 2 (or more) groups to test a specific drug, treatment or other intervention. One group (the experimental group) has the intervention being tested, the other (the comparison or control group) has an alternative intervention, a dummy intervention (placebo) or no intervention at all. The groups are followed up to see how effective the experimental intervention was. Outcomes are measured at specific times and any difference in response between the groups is assessed statistically. This method is also used to reduce bias.

  • Real-world data

    Data collected outside the context of a highly controlled clinical trial. Real-world data can be routinely collected during the delivery of health or social care. It can also be collected prospectively, to address 1 or more specific research questions.

  • Real-world evidence

    Evidence generated from the analysis of real-world data. This includes studies using real-world data to form an external control to a clinical trial.

  • Real-world evidence (RWE) framework

    This framework helps people developing evidence to inform NICE guidance. It uses real-world data to resolve gaps in knowledge and improve access to innovations for patients.

  • Reference case

    The methods NICE considers to be most appropriate for estimating clinical effectiveness and value for money.

  • Relative risk

    The probability of an event occurring in the study group compared with the probability of the same event occurring in the control group, described as a ratio. If both groups face the same level of risk, the relative risk is 1. If the first group had a relative risk of 2, subjects in that group would be twice as likely to have the event happen. A relative risk of less than 1 means the outcome is less likely in the first group. Relative risk is sometimes referred to as risk ratio. It will be very similar to the odds ratio when events are rare.

  • Relative treatment effect

    The effect of a treatment relative to another treatment or control, for example measured by relative risk (RR).

  • Reliability

    The ability to get the same or similar result each time a study is repeated with a different population or group.
  • Remuneration and terms of service committee

    A subcommittee of NICE's Board that sets the salaries and terms of service for senior staff.

  • Research recommendations

    Recommendations for future research covering questions relating to an uncertainty or lack of evidence that has been identified while developing NICE guidance.

  • Residential or day care settings

    Examples of residential and day care settings include:

    • day care centres for older people and adults or children with physical or learning disabilities
    • children’s homes
    • residential and nursing care homes (including those for adults and children with physical or learning disabilities)
    • prisons
    • young offender institutes.
  • Resolution process

    Before interventional procedures, medical technology or diagnostics guidance is published, consultees can ask for a 'resolution' if they think that the guidance is inaccurate or the process for developing interventional procedures guidance has not been followed. During the resolution process any concerns raised by the consultees are investigated.
  • Resource use

    Use of health and social care staff time, facilities, or consumables (including medicines), and anything else that can be used for providing healthcare services.

  • Respondent

    Tobacco organisations (for example, tobacco companies, those who speak for them or are funded by them) with an interest in a particular topic. The term ‘respondent’ acknowledges NICE’s commitment to Article 5.3 of the WHO Framework Convention on Tobacco Control. This sets out an obligation to protect the development of public health policy from any vested interests of the tobacco industry.

  • Retrospective study

    A research study that focuses on the past and present. The study examines past exposure to suspected risk factors for the disease or condition. Unlike prospective studies, it does not cover events that occur after the study group is selected.
  • Reverse causation

    Where the direction of causal effect is from the outcome (or symptoms thereof) to the intervention or exposure.

  • Review date

    The date at which NICE plans to start seeing if guidance needs to be updated. If this check finds a large amount of new evidence has been produced since the original guidance, NICE may propose that all or part of the guidance is updated.

  • Review of the literature

    A summary of the evidence in a number of different individual studies, with conclusions about their findings. A review may or may not be systematically researched and developed.
  • Review protocol

    A document that outlines the background, objectives and planned methods for a systematic review.
  • Risk factor

    Any aspect of a person's lifestyle, environment or pre-existing health condition that may increase their risk of developing a specific disease or condition.

  • Risk management committee

    A subcommittee of NICE's board that advises staff on identifying risks to the organisation and how to reduce them. Its work includes making sure NICE follows legislation on issues such as health and safety and data protection, and advising on preventing errors in published guidance.