Browse the glossary:
Searching for “cohort study”
142 matches found
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cohort study
(longitudinal study, prospective study, retrospective study)
— A type of non-randomized study in which defined groups of people (cohort) are followed up over time to explore the effects of treatments or other factors that may affect health outcomes; … (read more)
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before-after study
(before and after study, uncontrolled before and after study, uncontrolled before-after study)
— A type of non-randomized study in which health conditions are measured before and after a treatment; … (read more)
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case-control study
(matched pair study)
— A type of non-randomized study comparing the characteristics of people with a particular health condition (cases) with the characteristics of people without that condition (controls), to find what may have caused the problem; … (read more)
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interrupted time series study
(interrupted time series analysis, ITS study)
— A type of non-randomized study that measures an outcome at multiple time points before and after a treatment (the ”interruption”); … (read more)
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non-randomized study
(non-experimental study, observational study,)
— A category of studies that does not use random allocation to assign participants to treatment comparison groups; … (read more)
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controlled before-after study
(controlled before and after study, CBA study,)
— A type of non-randomized study in which outcomes are measured before and after a treatment, both in a group that receives the treatment and in another comparison group; … (read more)
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cross-sectional study
(disease frequency survey, prevalence study)
— A study measuring the distribution of a health condition, or other characteristics in a population at a particular point in time; … (read more)
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controlled study
— A study with two or more treatment comparison groups; … (read more)
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type of study
(research design)
— Key features of research methods used to categorize types of studies; … (read more)
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paired study design for diagnostic tests
(diagnostic paired design)
— A study design where two screening or diagnostic tests are compared and all patients receive both an index test and a reference standard test; … (read more)
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study participants
(subjects*, participants)
— The people included in a study; … (read more)
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study population
— All of the participants in a study; … (read more)
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protocol or study plan
— The document providing detailed plans for a study; … (read more)
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comparative study
— Any study that compares two or more treatments or factors; … (read more)
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parallel group study
— A type of study in which two or more groups of participants receive different treatments at the same time; … (read more)
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repeated measures study
— A type of non-randomized study, similar to an interrupted time series study, in which outcomes are measured in the same participants at multiple time points; … (read more)
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crossover study
(crossover trial)
— A type of randomized study in which the effects of two or more treatments are compared by giving them in different order (determined randomly) to each participant; … (read more)
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factorial study
(factorial design, factorial trial)
— A type of randomized study in which the effects of two or more treatments are compared by giving them separately, together, or not at all; … (read more)
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multicentre study
— A study in which several sites (e.g. hospitals or primary care clinics) collaborate; … (read more)
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qualitative study
(qualitative research)
— A study based on analyses of interviews, focus groups or observations used for gathering non-numerical data to describe social phenomena, such as experiences of health problems and treatments; … (read more)
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quantitative study
(quantitative research)
— A study based on analyses of numerical data; … (read more)
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randomized study
(randomized control trial, RCT, randomized trial, randomized controlled trial (should not be used))
— A category of studies comparing two or more treatments in which random allocation is used to assign participants to treatment comparison groups; … (read more)
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study
(evaluation, test, test of treatments, treatment comparison, treatment test, trial)
— An investigation using specified methods to answer a research question; e.g. about the effects of treatments; … (read more)
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cluster randomized study
(cluster randomized trial, cluster randomized controlled trial, group randomized trial)
— A treatment comparison in which pre-existing groups of people (e.g. hospitals) are randomly allocated to one or more treatment comparison groups; … (read more)
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direct comparison
(head-to-head comparison, within study comparison)
— A study in which the treatments or diagnostic tests of interest are evaluated in the same study; … (read more)
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case report
(case study)
— A study describing one person with a particular health condition, often covering the course of the problem before and after treatment; … (read more)
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adherence
(compliance, concordance)
— The degree to which participants in a study follow treatment instructions; … (read more)
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allocation
(assignment)
— The process of assigning participants in a study to treatment comparison groups.; … (read more)
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allocation schedule
(allocation sequence)
— The assignment of participants in a study to receive one of two or more treatments (including placebo, or no treatment) in a treatment comparison.; … (read more)
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allocation schedule concealment
(allocation sequence concealment, concealment of allocation)
— Methods used to prevent knowledge beforehand of which participants will be allocated to which treatments in a study.; … (read more)
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intention-to-treat analysis
— Analyses based on the outcomes in all the study participants allocated to each of the treatment comparison groups.; … (read more)
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interim analysis
— Analyses done to check that it is reasonable for an ongoing study to continue; … (read more)
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subgroup analysis
— Analyses restricted to selected groups of participants in a study to assess whether effect estimates vary across subgroups.; … (read more)
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applicability
(external validity, generalizability, relevance)
— The degree to which the results of a [.study] may apply to people who did not participate in the study; … (read more)
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attrition bias
(exclusion bias)
— Systematic differences between treatment comparison groups in withdrawals or exclusions of participants from the results of a study.; … (read more)
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disease progression bias
— In a study of diagnostic test accuracy, bias which occurs when the time period between the reference standard test and index test is so long that the health condition of interest may have changed between the two tests.; … (read more)
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spin
(interpretation bias)
— Bias resulting from interpreting the results of a study in a way which goes beyond an objective assessment of the evidence.; … (read more)
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measurement bias
(ascertainment bias, detection bias, observer bias)
— Bias resulting from systematic differences in how outcomes are measured in treatment comparison groups in a study.; … (read more)
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performance bias
— Bias resulting from differences in the care provided to the participants in a study, other than the treatments being compared.; … (read more)
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sponsor bias
— Bias resulting from the conduct of a study, or the interpretation of results, motivated by financial or academic vested interests.; … (read more)
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blinding
(masking)
— In treatment comparisons, actions intended to prevent study participants (the people receiving and providing care) or the researchers (or others measuring outcomes) from knowing which participants received which treatment; … (read more)
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double blinding
(double masking*)
— Actions intended to prevent two (or more) groups of people involved in a study knowing which participants received which treatment; … (read more)
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single blinding
(single masking)
— Actions intended to prevent one group of people involved in a study knowing which participants received which treatment; … (read more)
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triple blinding
(triple masking)
— Actions intended to prevent three (or more) groups of people involved in a study from knowing which participants received which treatment; … (read more)
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research data
(empirical data, empirical evidence)
— Information gathered in studies to help address research questions, such as assessing treatment effects; … (read more)
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data collection
— The process of gathering information in studies to help address research questions, such as assessing treatment effects; … (read more)
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difference
(absolute effect, risk difference)
— The difference in outcome between treatment comparison groups in a study; … (read more)
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relative effect
— The ratio of outcome measures in one treatment comparison group compared to another in a study; … (read more)
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eligibility criteria
(inclusion criteria, participation criteria, qualification criteria, selection criteria)
— Characteristics used to decide whether people are eligible to participate in a study and should be invited to participate; … (read more)
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enrolment
(inclusion)
— The act of including participants in a study when they meet explicit eligibility criteria; … (read more)
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unit of analysis error
— A type of error affecting the results of a study, usually a cluster-randomized trial, when the units used in the analysis of the results are different from the units of allocation to the treatment comparison groups; … (read more)
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level of evidence
(hierarchy of evidence)
— An indication of where a type of study lies in a hierarchy of evidence, based on the risk of bias; … (read more)
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extrapolated evidence
— Application of study results to people, treatments or outcomes that were not included in the study; … (read more)
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follow-up
(post-treatment outcome measurement)
— In treatment comparisons, assessment of study participants after treatment, or the length of time that participants are observed after being allocated to a treatment comparison group; … (read more)
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forest plot
— A graphical display of estimates, such as the effect estimates from each study included in a meta-analysis, together with the overall results; … (read more)
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indirect comparison
— Comparison across studies, in contrast to direct comparison within studies; … (read more)
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modified intention-to-treat analysis
— An analysis of study results that excludes some participants; … (read more)
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multiple statistical comparisons
— The application of many tests of the statistical significance of associations when analysing the results of a study; … (read more)
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single participant trial
(single case design)
— A study in which different treatments are allocated at random to be taken at different times by one person; … (read more)
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surrogate outcome
(proxy outcome, substitute outcome)
— Outcomes measured in a study, which are not of direct practical importance but are believed to reflect outcomes that are important; … (read more)
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placebo
— An inert substance, device or procedure used as a comparator in studies assessing the effects of a treatment; … (read more)
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planned analysis
— Analyses planned before starting data collection and pre-specified in study protocols; … (read more)
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p-value
— The probability (ranging from 0 to 1) that the results observed in a study could have occurred by the play of chance; … (read more)
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reproducibility
(repeatability, replicability)
— The extent to which the results of studies are confirmed in the results of subsequent studies; … (read more)
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sample size
— The actual or intended number of participants in a study; … (read more)
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selection criteria
(eligibility criteria, exclusion criteria, inclusion criteria)
— In systematic reviews, characteristics of studies used to decide whether they should be included; … (read more)
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statistical power
— In treatment comparisons, the likelihood that a study will be able to record sufficient outcome data to yield a statistically reliable measure of treatment effects; … (read more)
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phase 1 trial
— A research study designed to find out how a new drug is dealt with by the body, how the people given it react to it, and the lowest dose that may be effective; … (read more)
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low risk of bias
(internal validity)
— In studies of treatment effects, the extent to which the design and conduct of a study eliminates or reduces bias; … (read more)
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baseline characteristics
(baseline data)
— Descriptive information about the participants in a study collected at the beginning of the study.; … (read more)
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reporting bias
(publication bias)
— Bias resulting from decisions by researchers, or others (e.g. drug companies or journal editors) not to report or publish the results of a study, or not to provide full information about a study; … (read more)
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adverse event
(adverse effects, undesirable treatment effects)
— Unwanted symptoms or other experiences in participants in a study, which may or may not be caused by treatments.; … (read more)
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non-random allocation
(quasi-random allocation)
— Methods of allocating study participants to treatment comparison groups that are not random, but are intended to produce similar groups.; … (read more)
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association
(relationship, correlation)
— A relationship between two variables in a study, e.g. between having received a particular treatment and having experienced a particular outcome.; … (read more)
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bias
(systematic error)
— A type of error that may affect the results of a study because of weaknesses in its design, analysis or reporting.; … (read more)
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allocation bias
(assignment bias, selection bias)
— Bias resulting from the way participants in a study have been allocated to treatment comparison groups.; … (read more)
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case series
— A study describing several people with a particular health condition, often covering the course of the problem before and after treatment; … (read more)
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comparing like with like
(group equivalence)
— In treatment comparisons, making sure that groups of participants being compared in a study are as similar as possible in all ways other than the treatments being compared.; … (read more)
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incremental cost-effectiveness ratio
(ICER)
— The difference in cost of two treatments being compared in a study in relation to the difference in their effects; … (read more)
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data fishing
(data dredging, data-driven analysis)
— Analyses of information gathered in a study without predefined ideas of what to look for; … (read more)
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disease status
— Classification of a participant in a study as with or without a health condition of interest; … (read more)
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dramatic treatment effect
— Treatment effect that is so large that it is unlikely to be explained away by bias, even without having been tested in a study designed to minimize bias; … (read more)
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effectiveness
(clinical effectiveness, efficacy*)
— The extent to which a treatment has desirable effects in a study; … (read more)
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research evidence
(research findings, research results)
— The findings of studies, including systematic reviews; … (read more)
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fair comparisons of treatments
— Studies designed, conducted, reported and interpreted to minimize bias and the play of chance in measuring treatment effects; … (read more)
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imprecision
— The extent of the likely effect of the play of chance on the results of a study, meta-analysis or measurement; … (read more)
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inconsistency
(heterogeneity, variability)
— In treatment comparisons, unexplained variation in effect estimates among similar studies; … (read more)
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index test
— A diagnostic test that is being evaluated against a reference standard test in a study of test accuracy; … (read more)
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indirectness
— The extent to which studies do not directly compare the treatments of interest in populations of interest and measure outcomes of interest; … (read more)
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informed consent
— A process through which potential participants in a study are made aware of its purpose and the implications for them, and are invited to agree to participate; … (read more)
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likelihood
(probability, risk)
— The probability that an event, association, or difference will occur in a study or in practice; … (read more)
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loss to follow-up
(attrition, drop-outs)
— The loss of participants during the course of a study; … (read more)
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meta-analysis
— Statistical combination of estimates derived from two or more similar studies, to give an overall effect estimate; … (read more)
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minimization
— A method used for allocating participants to treatments in a study, aiming to achieve balance between treatment comparison groups in respect of factors that are expected to affect outcomes; … (read more)
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outcome
(outcome measure)
— In treatment comparisons, a good or bad event or development that can happen after a treatment, and is measurable in studies; … (read more)
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outcome measured on a scale
(continuous outcome)
— Outcomes in a study measured on a scale with a potentially infinite number of possible values within a given range; … (read more)
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secondary outcome
— Outcomes measured in a study, which were pre-specified as less important than the primary outcomes; … (read more)
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double dummy
(double dummy placebo)
— The use of two different placebos to achieve blinding when the treatments being compared in a study are obviously different; e.g. a tablet and an injection; … (read more)
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precision
— The extent to which errors due to the play of chance on the results of a study are likely to have occurred; … (read more)
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stratified randomization
(stratification, stratified allocation)
— The process of assigning participants in a study to treatment comparison groups based on characteristics (strata) thought to affect their prognosis; … (read more)
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resource use
— In treatment comparisons, all the important items and people used to deliver a treatment, and which may differ between the treatment comparison groups in a study; … (read more)
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subgroup
— A subset of a participants in a study or a population who share one or more specified characteristics; e.g. women or children; … (read more)
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systematic review
— A summary of studies addressing a clear question, using systematic and explicit methods to identify, select, and critically appraise relevant studies, and to collect and analyse data from them; … (read more)
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target condition
— The health condition of interest that a test is used to detect in a study of diagnostic test accuracy; … (read more)
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treatment comparison group
(arms of a trial, comparison group,)
— A group of participants in a study allocated to receive one or more different treatments, usual care, or placebo; … (read more)
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explanatory trial
(efficacy* trial)
— A study designed to assess the effects of a treatment given in ideal circumstances; … (read more)
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pragmatic trail
(effectiveness trial)
— A study designed to assess the effects of a treatment given in the circumstances of everyday practice; … (read more)
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phase 2 trial
— A study designed to find out whether a new drug is promising, to identify common side effects, and refine the dose and duration of treatment; … (read more)
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phase 3 trial
— A study designed to find out whether a promising new drug actually has important beneficial effects and an acceptable frequency and severity of side effects; … (read more)
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phase 4 trial
(post-marketing surveillance)
— A study carried out after a drug has received a marketing licence, to find out more about its effects, including long term harms and benefits; … (read more)
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random allocation
(randomization, random selection)
— The process of assigning participants in a study to treatment comparison groups using a chance process, like drawing lots, to protect against bias.; … (read more)
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acceptability
— How much a treatment or recommendation is accepted by the people who are affected by it, or who are implementing it, in a study or in practice; … (read more)
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exploratory analysis
— Analyses not intended to provide definitive evidence, but rather to suggest directions for future research.; … (read more)
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average difference
(mean difference)
— The difference between the average value of a measure (e.g. weight) in one group and the average value of the same measure in another group; … (read more)
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contamination
— In treatment comparisons, the inadvertent application of a treatment allocated to one comparison group to people in another comparison group; … (read more)
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critical assessment
(critical appraisal, critical review)
— Judging the risk of bias, results and applicability of evidence; … (read more)
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diagnosis
— The recognition or identification of a health condition based on symptoms, signs, or test results; … (read more)
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adverse effect
(harm)
— Unwanted symptom or other experience in participants which happen as a result of a treatment or test; … (read more)
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nocebo effect
— Undesirable effect that is or could be caused by an inactive treatment, presumed to act psychologically through suggestion; … (read more)
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effect estimate
(effect size, estimate of effect, point estimate)
— A statistical measure indicating the most likely size of a treatment effect; … (read more)
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estimate
— The most likely size of something; … (read more)
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monitoring
— Checking and recording specified measures; … (read more)
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odds
— In treatment comparisons, a statistical measure of the number of people in a treatment comparison group experiencing an outcome divided by the number not experiencing it; … (read more)
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odds ratio
(OR)
— A statistical measure of the odds of an outcome in one treatment comparison group divided by the odds in another comparison group; … (read more)
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primary outcome
(main outcome, primary end point,)
— Outcomes measured in treatment comparisons, which have been pre-specified as the most important in looking for potential benefits or harms of the treatments being compared; … (read more)
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objective outcome
(objective measure)
— An outcome less open to interpretation by potentially biased observers; … (read more)
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placebo effect
— Desirable effects that are or could be caused by an “inactive” treatment, presumed to act psychologically through suggestion; … (read more)
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prognosis
— The usual course and outcome of a condition; … (read more)
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random
— By chance, not predictable; … (read more)
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reference standard test
(gold standard, reference test)
— The best available method of determining whether people have a condition; … (read more)
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reliability
— The extent to which a claim or evidence about a treatment effect is trustworthy; … (read more)
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research methods
(methods)
— The systematic and transparent steps and protocols researchers follow to address research questions; … (read more)
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statistically significant
— A result that is unlikely to have happened by chance. The usual threshold for this judgement is a likelihood of less than 5%; … (read more)
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true negative test result
(true negative)
— For tests, a true negative result is when the index test result is negative and the reference standard test result is negative; … (read more)
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true positive test result
(true positive)
— For tests, a true positive result occurs when the index test is positive and the reference standard test result is also positive; … (read more)
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time horizon
— In economic evaluations, the time period specified over which important differences in resource use (costs) and outcomes are expected to occur; … (read more)
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false negative test result
(beta, false negative, type 2 error)
— Mistakenly concluding that there is no difference in effect between treatments, or between a treatment and no treatment, when there actually is; … (read more)
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variables
(characteristics, entities)
— Any measurable characteristic that varies; … (read more)
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false negative test result (duplicate)
— For tests, a false negative result is when the index test result is negative, while the reference standard test result is positive; … (read more)
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false positive test result (duplicate)
— For tests, a false positive test result occurs when the index test result is positive, while the reference standard test is negative; … (read more)
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confidence interval
(CI, margin of error,)
— A measure of uncertainty due to the play of chance; … (read more)
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play of chance
(random error)
— In treatment comparisons, a type of error that may affect the results because too few events or outcomes have been observed to provide a reliable measure of the treatment effects; … (read more)