Glossary ======== **Blinding (masking)**: in an experimental study, refers to whether patients, clinicians providing an intervention, people assessing outcomes, and/or data analysts were aware or unaware of the group to which patients were assigned. In the design section of *Evidence-Based Nursing* abstracts of treatment studies, the study is identified as *blinded*, with specification of who was blinded; *unblinded*, if all parties were aware of patients’ group assignments; or *blinded (unclear)* if the authors did not report or provide us with an indication of who was aware or unaware of patients’ group assignments. **Concealment of randomisation:** concealment of rando-misation is specified in the design section of *Evidence-Based Nursing* abstracts of treatment studies as follows: *allocation concealed* (deemed to have taken adequate measures to conceal allocation to study group assignments from those responsible for assessing patients for entry in the trial [ie, central randomisation; sequentially numbered, opaque, sealed envelopes; sealed envelopes from a closed bag; numbered or coded bottles or containers; drugs prepared by the pharmacy; or other descriptions that contain elements convincing of concealment]); *allocation not concealed* (deemed to have not taken adequate measures to conceal allocation to study group assignments from those responsible for assessing patients for entry in the trial [ie, no concealment procedure was undertaken, sealed envelopes that were not opaque or were not sequentially numbered, or other descriptions that contained elements not convincing of concealment]); *unclear allocation concealment* (the authors did not report or provide a description of an allocation concealment approach that allowed for the classification as concealed or not concealed). **Confidence interval (CI)**: quantifies the uncertainty in measurement; usually reported as 95% CI, which is the range of values within which we can be 95% sure that the true value for the whole population lies. **Data saturation (saturation, redundancy)**1: process of collecting data in a qualitative research study to the point where no new themes are generated. **Diagnostic (gold or criterion) standard**: the current best available measure of an outcome; used for assessing properties of a new diagnostic or screening test. The results from a new test are compared with the results from the diagnostic standard to assess the usefulness of the new test (ie, its sensitivity, specificity, and likelihood ratios). **Fixed effects model**2: gives a summary estimate of the magnitude of effect in meta-analysis. It takes into account within-study variation but not between-study variation and hence is usually not used if there is significant heterogeneity. **Hazard ratio**3: the weighted relative risk over the entire study period; often reported in the context of survival analysis **Heterogeneity**2: the degree to which the effect estimates of individual studies in a meta-analysis differ significantly. **Intention to treat analysis (ITT)**: all patients are analysed in the groups to which they were randomised, even if they failed to complete the intervention or received the wrong intervention. **Likelihood ratio (for positive and negative results)**4: a way of summarising the findings of a study of a diagnostic test for use in clinical situations where there may be differences in the prevalence of the disease. The likelihood ratio for a positive test is the likelihood that a positive test result comes from a person that really does have the disorder rather than one that does not have the disorder (sensitivity/1 − specificity). The likelihood ratio for a negative test is the likelihood that a negative test result comes from a person with the disorder rather than one without the disorder (1 − sensitivity/specificity). **Number needed to harm (NNH)**5: number of patients who, if they received the experimental treatment, would lead to 1 additional person being harmed compared with patients who receive the control treatment; this is calculated as 1/absolute risk increase (rounded to the next whole number), accompanied by the 95% confidence interval. **Number needed to treat (NNT)**: number of patients who need to be treated to prevent 1 additional negative event (or to promote 1 additional positive event); this is calculated as 1/absolute risk reduction (rounded to the next whole number), accompanied by the 95% confidence interval. **Odds ratio (OR)**: describes the odds of a patient in the experimental group having an event divided by the odds of a patient in the control group having the event *or* the odds that a patient was exposed to a given risk factor divided by the odds that a control patient was exposed to the risk factor. **Relative benefit increase (RBI)**: the proportional increase in the rates of good events between experimental and control participants; it is reported as a percentage (%). **Relative risk (RR)**: proportion of patients experiencing an outcome in the treated (or exposed) group divided by the proportion experiencing the outcome in the control (or unexposed) group. **Relative risk increase (RRI):** the proportional increase in bad outcomes between experimental and control participants; it is reported as a percentage (%). **Relative risk reduction (RRR)**: the proportional reduction in bad outcomes between experimental and control participants; it is reported as a percentage (%). **Sensitivity**5: a measure of a diagnostic test’s ability to correctly detect a disorder when it is present in a sample of people. **Specificity**5: a measure of a diagnostic test’s ability to correctly identify the absence of a disorder in a sample of people who do not have the disorder. **Weighted mean difference**2: in a meta-analysis, used to combine outcomes measured on continuous scales (eg, height), assuming that all trials measured the outcome on the same scale; the mean, standard deviation, and sample size of each group are known, and weight given to each trial is determined by the precision of its estimate of effect. ## References 1. Polit DF, Beck CT, Hungler BP. *Essentials of nursing research: methods, appraisal, and utilization,* Fifth edition. Philadelphia: Lippincott, 2001. 2. Clarke M, Oxman AD, editors. Glossary. Cochrane reviewers’ handbook 4.1.2 (updated March 2001). In: *Cochrane Library*. Oxford: Update Software. Updated quarterly. 3. Guyatt G, Rennie D, editors. *Users’ guides to the medical literature.* A manual for evidence-based clinical practice. Chicago: American Medical Association, 2002. 4. Streiner D, Geddes J. Some useful concepts and terms used in articles about diagnosis [editorial]. Evidence-Based Mental Health 1998;1:6–7. [FREE Full Text](http://ebn.bmj.com/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiRlVMTCI7czoxMToiam91cm5hbENvZGUiO3M6ODoiZWJtZW50YWwiO3M6NToicmVzaWQiO3M6NToiMS8xLzYiO3M6NDoiYXRvbSI7czoyMToiL2VibnVycy83LzEvMzIuMi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=) 5. Sackett DL, Haynes RB, Guyatt GH, *et al*. *Clinical epidemiology: basic science for clinical medicine*, Second edition. Boston: Little, Brown and Company, 1991.