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)
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)
parallel group study
— A type of study in which two or more groups of participants receive different treatments at the same time; … (read more)
partial reference bias
— When only a proportion of the study group receive both the index and reference standard test when investigating for diagnostic accuracy.; … (read more)
participants see study participants
(subjects*, participants)
— The people included in a study; … (read more)
peer review
— An editorial process for assessing the quality and importance of research reports submitted for possible publication; … (read more)
perception bias
— The tendency to be subjective about people and events, causing biased information to be collected in a study or biased interpretation of a study’s results.; … (read more)
performance bias
— Systematic differences in the care provided to members of different study groups other than the intervention under investigation.; … (read more)
perspective
(analytic perspective, viewpoint)
— In guideline recommendations or economic evaluations, the viewpoint that is adopted, which determines the factors (e.g. costs, effects, acceptability) that are included; … (read more)
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)
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)
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)
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)
see PICO
(PICOT)
— Commonly used acronym for the key components of a research question: Patient (or population), Intervention (treatment, test or exposure), Comparison, and Outcome; … (read more)
placebo
— An inert substance, device or procedure used as a comparator in studies assessing the effects of a treatment; … (read more)
placebo effect
— Desirable effects that are or could be caused by an “inactive” treatment, presumed to act psychologically through suggestion; … (read more)
placebo, double dummy see 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)
planned analysis
— Analyses planned before starting data collection and pre-specified in study protocols; … (read more)
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)
popularity bias
— Differences in the uptake of healthcare as a result of a public interest in a disease or condition and its possible causes results in a biased study sample.; … (read more)
positive predictive value
(PPV)
— The proportion of people with a positive test result who have the target condition of interest; … (read more)
positive results bias
— The tendency to submit, accept and publish positive results rather than non-significant or negative results.; … (read more)
pragmatic trail
(effectiveness trial)
— A study designed to assess the effects of a treatment given in the circumstances of everyday practice; … (read more)
pre-test probability
(prevalence)
— For screening and diagnostic tests, the likelihood that someone has the target condition for which the test is being used; … (read more)
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)
predictive value, negative see negative predictive value
(NPV)
— The proportion of people with a negative test result who do not have the disease or target condition of interest; … (read more)
prevalence
— The proportion of a population having a particular condition or characteristic; … (read more)
prevalence-incidence (Neyman) bias
(Neyman bias)
— Exclusion of individuals with severe or mild disease resulting in a systematic error in the estimated association or effect of an exposure on an outcome.; … (read more)
previous opinion bias
— The results of a previous assessment, test result or diagnosis, if known, may affect the results of subsequent processes on the same patient.; … (read more)
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)
prognostic variable
(prognostic marker)
— A characteristic or combination of characteristics known to be associated with the course of a health condition; … (read more)