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 *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 randomisation 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. **Constant comparison**1: a procedure used in qualitative research wherein newly collected data are compared in an ongoing fashion with data obtained earlier, to refine theoretically relevant categories. **Data saturation (saturation, redundancy)**1: process of collecting data in a qualitative research study to the point where no new themes are generated. **Ethnography (ethnographic study)**1: an approach to inquiry that focuses on the culture or subculture of a group of people, with an effort to understand the world view of those under study. **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. **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. **Number needed to harm (NNH)**4: 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. **Random effects model**2: gives a summary estimate of the magnitude of effect in meta-analysis. It takes into account both within-study and between-study variance and gives a wider confidence interval to the estimate than a fixed effects model if there is significant between-study variation. **Receiver operating characteristic (ROC) curve**5: an analysis used to assess the clinical usefulness of a diagnostic or screening test. It yields a score that has the highest rates of both sensitivity and specificity with respect to a diagnosis—that is, a score that will give the maximum rate of accurate classifications. **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 analysis:** tests the robustness of the observed results relative to sensible modifications in important variables. **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. Sackett DL, Haynes RB, Guyatt GH, *et al.* Clinical epidemiology: basic science for clinical medicine. Second edition. Boston: Little, Brown and Company, 1991. 5. Steer RA, Cavalieri TA, Leonard DM, *et al.* Use of the Beck Depression Inventory for Primary Care to screen for major depression disorders. Gen Hosp Psychiatry 1999;21:106–11. 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