Nomenclature follows the standard international nomenclature for meridians; an alphabetic code agreed at a meeting of the WHO Scientific Group in 1989.
Bias
Deviation of results from the truth or mechanisms leading to such deviation (e.g. analysis bias, measurement bias, publication bias, selection bias, withdrawal bias and others). In clinical studies, bias is mainly controlled by blinding and randomisation.
Blinding
Study participants and/or study staff (therapists, outcome assessors) are unaware of who receives the experimental or control treatment.
Cohort
A group of individuals with some characteristics in common who are followed over time to see who develops a disease or outcome, and factors associated with this.
Complementary and alternative medicine
Includes all such practices and ideas which are outside the domain of conventional medicine in several countries and defined by its users as preventing or treating illness, or promoting health and well-being. These practices complement mainstream medicine by (1) contributing to a common whole; (2) satisfying a demand not met by conventional practices; and (3) diversifying the conceptual framework of medicine. (CAM definition adopted by the Cochrane Complementary Medicine Field)
Confidence interval
Quantifies the uncertainty in measurement. Usually reported as 95 % CI, which is the range of values within which one can expect to find the true value in 95 % of cases.
Controlled trial
Control is a standard against which experimental observations may be evaluated. In clinical trials, one group of participants is given an experimental intervention, while another group (i.e. the control group) is given either a standard treatment for the disease, a placebo or no treatment at all.
Crossover
Participants in the intervention group receive the control treatment upon completion of the treatment cycle. Similarly those in the control group ‘crossover’ and receive the experimental intervention.
Double-blind trial
A clinical trial design in which neither the participating individuals nor the study staff know which participants are receiving the experimental treatment and which are receiving the control treatment or placebo. Double-blind trials are thought to produce objective results, since the expectations of the participants and study staff about the experimental drug do not affect the outcome.
Intention-to-treat analysis
Data are analysed according to original intervention assignment of participants, whether or not they complete/receive treatment.
Meta-analysis
A quantitative statistical method to pool trial data in a single estimate. Can be part of a systematic review.
Number needed to treat
Number of patients who need to be treated to prevent one additional negative event (or to promote one additional positive event).
Odds ratio
Ratio of probability of an event in one group to probability of the event in a compared group.
Power
The ability to detect a clinically important difference if one exists. Power of a study increases with larger sample sizes and more precise measurement.
P-value
Probability that an observed difference between groups occurred by chance alone. A result is conventionally regarded as ‘statistically significant’ if the likelihood that it is due to chance alone is less than five times out of 100 (P 50.05).
Randomisation
The process by which patients in a clinical trial are randomly assigned to experimental intervention or control treatment. Randomisation minimises the differences among groups by equally distributing participants with particular characteristics (known or unknown) among all the trial arms.
Randomised clinical trial
Prospective study where participants are randomly allocated to receive experimental or control treatment.
Relative risk
Proportion of patients experiencing an outcome in the treated group divided by the proportion experiencing the outcome in the control group.
Standard deviation
A statistical measure of the distance a quantity is likely to lie from its average value (i.e. a measure of dispersion). The more widely the scores are spread out, the greater the standard deviation.
Standardised mean difference
In a systematic review, a way of combining the results of studies that may have measured the same outcome (e.g. pain) in different ways, using different scales. Effects are expressed as standard values with no units.
Systematic review
Review in which literature from multiple sources is systematically searched for, assessed and evaluated to answer clearly formulated questions.
