The NICE glossary provides brief definitions and explanations of terms and jargon used on our site. The terms describe how we work and how our guidance is produced.

Our glossary excludes specific clinical and medical terms although we intend to include these in the longer term. If you cannot find the term you are looking for, please email us so that we can consider adding it to the glossary. New terms are added regularly.

The glossary is not used for indexing the site or for navigation - for information on this, please see the NICE taxonomy.

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


P value

The p value is a statistical measure that indicates whether or not an effect is statistically significant.

For example, if a study comparing two treatments found that one seems more effective than the other, the p value is the probability of obtaining these results by chance. By convention, if the p value is below 0.05 (that is, there is less than a 5% probability that the results occurred by chance) it is considered that there probably is a real difference between treatments. If the p value is 0.001 or less (less than a 1% probability that the results occurred by chance), the result is seen as highly significant.

If the p value shows that there is likely to be a difference between treatments, the confidence interval describes how big the difference in effect might be.

Partners Council

A group of people representing organisations that have an interest in NICE's work. These organisations include patient groups, healthcare professionals, NHS management, drug and medical equipment manufacturers and trade unions. The Partners Council reviews NICE's annual report. It also discusses ideas and future plans for NICE.

Patient and Public Involvement Programme

A department in NICE that advises on involving patients and carers in NICE's work. It also supports patients and carers who are members of groups that produce guidance, and stakeholder organisations that are commenting on draft guidance.


See Primary Care Trust.

Peer review

Review of a study, service or recommendation by those with similar interests and expertise to the people who produced it to make sure the study results are accurate and valid. (Note: the review cannot guarantee that the results of the study will not be flawed - that is, prone to bias.) Peer reviewers can include both professionals and 'lay' experts. Lay experts are people whose expertise derives from their personal experience rather than formal training.

Performance bias

This can occur if study participants know which group they are in. For example, if they know they are in the control group they may use other forms of care. Similarly, if care providers know which group they are in, they may treat patients differently. Ensuring neither the recipients or providers of care know who is in which group (blinding) protects against performance bias.

Pilot study

A small-scale 'test' of a particular approach. For example, a new questionnaire could be piloted with a small group of people before it is sent out to a wider audience. The aim would be to highlight any problems or areas of concern and amend it before the full-scale study begins.


A fake (or dummy) treatment given to participants in the control group of a clinical trial. It is indistinguishable from the actual treatment (which is given to participants in the experimental group). The aim is to determine what effect the experimental treatment has had - over and above any placebo effect caused because someone has received (or thinks they have received) care or attention.

Placebo effect

A beneficial (or adverse) effect resulting from someone thinking they have been given a treatment. This can occur when people in the control group of a study take a placebo.


A group of people with a common link, such as the same medical condition or living in the same area or sharing the same characteristics. The population for a clinical trial is all the people the test or treatment is designed to help (such as adults with diabetes). The group taking part in a clinical trial need to be typical of the whole population of interest.


See statistical power.

Premeeting briefing

A document that summarises the findings from the evidence for a single technology appraisal. It is used at the meeting in which the Appraisal Committee writes the draft guidance.


Used to describe the proportion of people in a population who have a particular habit, a particular disease or another characteristic. For example, smoking prevalence relates to the proportion of people who smoke in a given population. Prevalence may be expressed in relation to a range of factors including age, sex, socioeconomic and ethnic group. See also incidence.

Primary care

Healthcare delivered outside hospitals. It includes a range of services provided by GPs, nurses, health visitors, midwives and other healthcare professionals and allied health professionals such as dentists, pharmacists and opticians.


How likely it is that an event will occur. For example, the likelihood that a treatment or intervention will help alleviate a health problem. See also odds ratio.


A series of actions designed with one aim in mind. In the case of NICE, the process is the actions involved in producing NICE guidance or other advice (such as implementation tools). When producing NICE guidance, the process includes: deciding what it will cover (the scope), setting up a group of experts who will look at the evidence and make recommendations, and a consultation with professionals and the public on draft guidance.

Prognostic factor

A characteristic of a disease or patient (age is an example of the latter) that influences how the disease being studied develops. In a randomised controlled trial comparing two treatments, chance differences in a prognostic factor (or variable) can influence the results of treatment. In such cases, they become confounding factors when the study is analysed. See also prognostic marker.

Prognostic marker

A characteristic that gives an indication of the likely progression of the disease among patients with the same characteristic. The purpose of randomisation in a clinical trial is to have treatment groups that have important prognostic factors in common. For example, if age was known to affect the outcome of treatment, then separate randomisation schemes would be used for different age groups.

Programme development group (PDG)

A group of health and other professionals and researchers, brought together to write a particular piece of public health guidance that is being developed using the public health programme process. The Centre for Public Health Excellence recruits the group, commissions reviews of the evidence and supports the group in its work. The group writes draft guidance, and then revises it after a consultation with organisations registered as stakeholders.

Prospective study

A research study in which the health or other characteristic of participants is monitored (or 'followed up') for a period of time, with events recorded as they happen. This contrasts with retrospective studies.


A plan or set of steps that defines how something will be done. Before carrying out a research study, for example, the research protocol sets out what question is to be answered and how information will be collected and analysed.

Public health intervention guidance

NICE public health intervention guidance is recommendations on types of activity (interventions) that help to reduce people's risk of developing a disease or condition or help to promote or maintain a healthy lifestyle. Examples of interventions would be giving advice, providing services or providing support, e.g. giving advice in GP practices to encourage exercise, providing a needle exchange scheme for injecting drug users, providing support for new mothers to enable the uptake and continuation of breastfeeding.

Public health intervention process

A process used to develop public health guidance on a particular activity or set of activities ('interventions') to promote or maintain a healthy lifestyle or reduce the risk of developing a disease or condition. For example, the guidance might cover advising people how to take more exercise and encouraging them to take the advice. The guidance is written by the Public Health Interventions Advisory Committee.

Public Health Interventions Advisory Committee (PHIAC)

An independent standing committee set up by NICE to write public health guidance that is being developed using the public health intervention process. The Committee usually meets twice to discuss each piece of guidance. The first time it produces the draft guidance, based on the research and discussion with experts. The second time it revises the guidance after a consultation period to produce the final document. The committee is made up of health professionals and other professionals involved in improving people's health (such as local authority environmental health officers), researchers and members of organisations representing the public. Committee members are appointed for 3 years.

Public health programme guidance

NICE public health programme guidance deals with broad action for the promotion of good health and the prevention of ill-health. This guidance may focus on a topic, such as smoking, or on a particular population, such as young people, or on a particular setting, for example, the workplace.

Public health programme process

A process used to develop public health guidance covering a broad range of activities to promote good health and prevent illness. This guidance may focus on a topic (such as strategies to help people give up smoking), or on a particular population (such as young people or pregnant women) or on a particular setting (for example, the workplace). It is written by a programme development group that is brought together for the particular piece of guidance.

Publication bias

Publication bias occurs when researchers publish the results of studies showing that a treatment works well and don't publish those showing it did not have any effect. If this happens, analysis of the published results will not give an accurate idea of how well the treatment works. This type of bias can be assessed by a funnel plot.

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This page was last updated: 15 April 2011

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Accessibility | Cymraeg | Freedom of information | Vision Impaired | Contact Us | Glossary | Data protection | Copyright | Disclaimer | Terms and conditions

Copyright 2014 National Institute for Health and Care Excellence. All rights reserved.