The NICE Glossary provides brief definitions and explanations of terms used on our site. The terms describe how we work and how our 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.

  • Baseline

    The initial set of measurements at the beginning of a study (after any initial 'run-in' period with no intervention), with which subsequent results are compared.
  • Benchmark

    A measure or standard that can be used to compare an activity, performance, service or result. 'Benchmarking' is the process of measuring the performance of people or organisations with broadly similar characteristics. The aim is to improve quality by encouraging all organisations or services to raise their own performance to that of the best.
  • Best available evidence

    The strongest, best-quality research evidence available on the topic being investigated.
  • Bias

    Systematic (as opposed to random) deviation of the results of a study from the 'true' results, which is caused by the way the study is designed or conducted.
  • Blinding or masking

    A way to prevent researchers, doctors and patients in a clinical trial from knowing which study group each patient is in so they cannot influence the results. The best way to do this is by sorting patients into study groups randomly. The purpose of 'blinding' or 'masking' is to protect against bias.
    In a single-blinded study, patients do not know which study group they are in (for example whether they are taking the experimental drug or a placebo). In a double-blinded study, neither the patients nor the researchers/doctors know which study group the patients are in. In a triple-blind study, the patients, clinicians and the people carrying out the statistical analysis do not know which treatment patients received.
  • Burden of disease study

    A study investigating the overall impact of diseases and injuries at the individual level, at the societal level or on the economic costs of diseases.
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