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.



Participants of a study recruited from part of the study's target population. If they are recruited in an unbiased way, the results from the sample can be generalised to the target population as a whole.


The way participants are selected for inclusion in a study.

Sampling frame

A list or register of names that is used to recruit participants to a study.


The scope is a short document that sets out what a NICE clinical guideline or piece of NICE public health guidance will and will not cover. A period of public consultation takes place before the scope is finalised.

Secondary care

Care provided in hospitals.

Selection bias

Selection bias occurs if:

a) The characteristics of the people selected for a study differ from the wider population from which they have been drawn, or

b) There are differences between groups of participants in a study in terms of how likely they are to get better.

Selection criteria

The criteria used to decide which studies should be included and excluded from consideration as potential sources of evidence when developing NICE guidance. It can also refer to a set of conditions that must be met for someone to take part in a clinical trial (such as age and sex).

Semi-structured interview

The interviewer asks a number of open-ended questions and follows up on areas of interest in response to the information given. It allows more flexibility than a structured interview, which involves asking pre-set questions.


How well a test detects the thing it is testing for.

If a diagnostic test for a disease has has high sensitivity, it is likely to pick up all cases of the disease in people who have it (that is, give a 'true positive' result). But if a test is too sensitive it will sometimes also give a positive result in people who don't have the disease (that is, give a 'false positive').

For example, if a test were developed to detect if a woman is 6 months pregnant, a very sensitive test would detect everyone who was 6 months pregnant, but would probably also include those who are 5 and 7 months pregnant.

If the same test were more specific (sometimes referred to as having higher specificity), it would detect only those who are 6 months pregnant, and someone who was 5 months pregnant would get a negative result (a 'true negative'). But it would probably also miss some people who were 6 months pregnant (that is, give a 'false negative').

Breast screening is a 'real-life' example. The number of women who are recalled for a second breast screening test is relatively high because the test is very sensitive. If it were made more specific, people who don't have the disease would be less likely to be called back for a second test but more women who have the disease would be missed.

Short clinical guideline

A clinical guideline produced using a 'fast track' process. Short clinical guidelines cover small, defined areas of patient care or a small sub-group of patients.

Single blind study

A study in which either the subject (patient or participant) or the observer (clinician or investigator) does not know which treatment or intervention the subject is receiving.

Single technology appraisal

Technology appraisal guidance, using a 'fast-track' process, for a single drug or treatment.

Slide set

A set of slides that local NHS staff can use to raise awareness of a piece of NICE guidance among healthcare professionals and managers.

Social marketing

Using marketing principles and techniques as part of a health promotion campaign to persuade people to make a positive change in their behaviour to improve their health or prevent ill health.

Socioeconomic status

Description of a person's position in society using criteria such as their occupation, income or level of education achieved.

Specialist adviser

People with specialist knowledge of the procedure being assessed for interventional procedures guidance. Specialist advisers are nominated by a relevant professional organisation to advise the Interventional Procedures Advisory Committee.

Specific indication

The particular condition that a drug or device is licensed to treat. See also off-label prescribing.


See sensitivity.

Stakeholder (see also Commentator and Consultee)

An organisation with an interest in a topic that NICE is developing a clinical guideline or piece of public health guidance on. Organisations that register as stakeholders can comment on the draft scopeand the draft guidance. Stakeholders may be:

  • manufacturers of drugs or equipment
  • national patient and carer organisations
  • NHS organisations
  • organisations representing healthcare professionals.
Standard deviation

A measure used to summarise numerical data and describe how 'spread out' a set of measures (or 'values') are from the average. For example, the average height of a group of schoolchildren can be calculated using the total of all their heights added together and then divided by the number of schoolchildren in the group. Standard deviation measures the 'spread' of those heights. So, in the example it tells you whether all those in the group were about the same height or whether some were very tall and some were short.

Statistical power

The ability of a study to demonstrate an association or causal relationship between two variables (if an association exists) means that the study is statistically significant. The statistical power of a study is primarily related to the number of people included. If too few people are included, any differences in the outcomes will not be statistically significant.

Structured interview

A research technique in which the interviewer asks all study participants a list of pre-set questions.

Study checklist

A set list of questions about the research methodology used to ensure a study is valid. A different checklist is used for each study type.

Study participant

A person who takes part in an experiment or research study. Also known as a subject.

Study population

People who are the subjects of a research study.

Study quality

See methodological quality.

Study type

The way a study is designed. Case-control study, cohort study, non-randomised controlled trial, and randomised controlled trial are all examples of study types using different research methodologies.


A person who takes part in an experiment or research study. Also known as a study participant.


A list of structured questions. The aim is to collect information systematically from people for a study. (Information is usually collected from a sample within a defined population.)


A document that summarises the evidence collated for a piece of public health guidance. It contains a brief introduction followed by summaries of each evidence review.


Methodical, not random.

Systematic error

Refers to the various errors or biases inherent in a study. See also bias.

Systematic review

A review in which evidence from scientific studies has been identified, appraised and synthesised in a methodical way according to predetermined criteria. It may include a meta-analysis.


Involving the whole body.


Systemic disease

A disease that affects the patient's whole body.

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This page was last updated: 15 April 2011

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Selected, reliable information for health and social care in one place

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.