Pre-Test Probability
The estimated probability that a patient has a condition before a diagnostic test result is known, based on prevalence and clinical presentation.
Encyclopaedia
Explore comprehensive, evidence-informed explanations of key health economics concepts, including their development, application and relationships to other concepts. Published entries are validated through human expert review.
Prediction Error
The difference between a value predicted by a statistical model and the value that is actually observed.
Prediction Interval
A range calculated to contain a future individual observation with a specified confidence, unlike a confidence interval describing a population parameter.
Prevalence
The total proportion of a population with a particular condition at a given time, covering both new and pre-existing cases.
Prevalence Difference
The absolute difference in the prevalence of a condition between two groups, giving a direct measure of disparity in disease burden.
Prevalence Ratio
A measure comparing the prevalence of a condition between two groups, calculated as the ratio of one group's prevalence to the other's.
Prevented Fraction
The proportion of disease cases avoided in a population due to a protective exposure or intervention, the counterpart to the attributable fraction.
Principal Component
In principal component analysis, a derived variable combining original observed variables to capture the maximum possible variance, uncorrelated with prior components.
Prior Distribution
In Bayesian statistics, the probability distribution representing existing beliefs about a parameter before observing new data.
Prior Odds
The odds that a hypothesis is true before incorporating new evidence, the starting point for Bayesian updating alongside a likelihood ratio.
Propensity Score
The estimated probability that an individual would receive a particular treatment given their observed characteristics, used to balance confounders in observational studies.
Propensity Score Matching
A statistical technique pairing treated individuals with similar untreated individuals based on an estimated propensity score, balancing measured confounding variables.
Quartile
A descriptive statistic dividing a ranked dataset into four equal-sized groups, marking the twenty-fifth, fiftieth, and seventy-fifth percentiles.
Random Effects
In a mixed effects model, the components representing how individual units, such as patients, vary around an overall average relationship.
Random Effects Model
A meta-analysis model allowing genuine variation in the true treatment effect across studies, adding a between-study variance parameter to the estimate.
Random Effects Synthesis
An approach combining evidence that explicitly allows for and estimates genuine variation in the true effect between studies, rather than assuming one common effect.
Randomization
The process of assigning trial participants to treatment groups by chance, producing groups comparable on both known and unknown influencing factors.
Range
A dispersion measure calculated as the difference between the maximum and minimum values in a dataset, sensitive to extreme outliers.
Rate Difference
The absolute difference between the incidence rates in two groups, giving a direct measure of the excess rate of disease from an exposure.
Rate Ratio
A measure comparing the incidence rates of an outcome between two groups, accounting for differences in person-time at risk.