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.
In a study, validity is the degree to which the conclusions that the researchers make can be considered to be 'true', based on how well the study was designed and how well it matched 'real life' situations. See also external validity, internal validity.
Variability refers to the differences that can be seen between people (or in the same person) over time. An example of the former could be the age, sex and genetic background of participants in a study.
This page was last updated: 15 April 2011