Probability mass function (pmf) - A probability mass function, or pmf, assigns a probability to each possible value of a discrete random variable.
Probability model - A probability model is a mathematical description of uncertain outcomes and the probabilities assigned to them.
Probability of direction - Probability of direction, usually abbreviated pd, summarizes which side of a specified reference value has more posterior probability.
Probability of error - Probability of error is the probability that a specified decision or prediction is incorrect under a stated probability model or population distribution.
Probability plot - A probability plot compares ordered observations with corresponding theoretical quantiles from a proposed probability distribution.
Probability proportional to size - Probability proportional to size, often abbreviated PPS, describes sampling designs in which selection probabilities are linked proportionally to a known...
Probability simplex - The probability simplex is the set of all vectors whose components are nonnegative and sum to one.
Probability space - A probability space is the mathematical structure used to describe uncertain outcomes and assign probabilities consistently.
Probability theory - Probability theory is the mathematical study of uncertainty using probabilities, events, random variables, and distributions.
Probalistic imputation - Probalistic imputation is the supplied glossary spelling for an imputation rule that partly depends on an external randomization process.
Probit model - A probit model is a regression model for a binary outcome that relates its probability to predictors through the standard normal cumulative distribution...
Proctor survey - A proctor survey is a survey administered to respondents gathered in a room with a person who supervises its administration.
Projection filters - Projection filters are approximate nonlinear filtering methods that represent an evolving conditional probability distribution within a chosen...
Projection pursuit - Projection pursuit is a family of methods that searches for low-dimensional linear projections of multivariate data that score highly on a chosen measure of...
Projection pursuit regression - Projection pursuit regression, or PPR, models a numerical response as a sum of flexible functions of linear combinations of predictors.
Proportion - A proportion expresses how much of a defined whole belongs to a particular category or meets a specified condition.
Proportional hazards - Proportional hazards is an assumption that the hazard functions for two groups or covariate profiles differ by a constant multiplicative factor over time.
Proportional reduction in error (PRE) - Proportional reduction in error, or PRE, measures how much a prediction rule reduces error relative to a specified baseline.
Proportionality - Proportionality, in the supplied factorial-analysis-of-variance context, is a condition on cell sample sizes: the relative distribution across levels of one...
Proportionate reduction of error - Proportionate reduction of error is a way of interpreting predictive association by comparing errors made without particular information with errors made...
Proposal distribution - A proposal distribution is a distribution used to generate candidate values in a sampling algorithm.
Prospective study - A prospective study is planned before participants or other study units are enrolled and followed for the outcomes of interest.
Pseudomedian - The pseudomedian is a measure of location defined as the median of the average of two independent observations from the same population.
Pseudoreplication - Pseudoreplication occurs when an analysis treats observations as independent replications of an effect even though the study design does not support that...
Pyrrho's lemma - Pyrrho's lemma is a result about the vulnerability of regression conclusions to a deliberately selected additional regressor.
Q-value (statistics) - A q-value is a measure of statistical significance designed for multiple hypothesis testing.
Qualitative data - Qualitative data describe types, qualities, or categories rather than measured amounts or counts.
Quantile - A quantile usually means a value marking a specified position in an ordered distribution, such as the median or the 90th percentile.
Quantile bucketing - Quantile bucketing divides a numerical feature into intervals intended to contain the same, or approximately the same, number of observations in a reference...
Quantile Regression - Quantile regression models a chosen quantile of an outcome conditional on explanatory variables.
Quantile regression averaging - Quantile regression averaging, or QRA, combines forecasts by using them as inputs to a quantile regression model.
Quantitative data - Quantitative data represent measured amounts or counts expressed numerically.
Questionnaire error - Questionnaire error is the part of survey measurement error attributable to a questionnaire's wording, structure, or form.
R chart - An R chart is a statistical process control chart that tracks the range within successive subgroups of measurements.
R-squared - R-squared, or the coefficient of determination, compares a regression model's squared prediction errors with the squared deviations of the observed outcomes...
Raleigh plot - A Raleigh plot, in the circular-data sense intended here, displays observations as positions around a circle and often adds their mean direction and mean...
Ramsey RESET test - The Ramsey RESET test is a regression diagnostic that looks for neglected nonlinear structure by adding functions of the original model's fitted values or...
Random error - Random error is the component of an estimate's or measurement's deviation that varies unpredictably across repetitions of a specified process.
Random marginal totals - Random marginal totals are row or column totals in a contingency table whose values are not fixed by the sampling design and can vary across repeated data...
Random model Anova - A random model ANOVA, more commonly called a random-effects analysis of variance, treats the effects of factor levels as draws from a population of possible...
Random perturbation - Random perturbation, in statistical disclosure control, deliberately changes data using a random mechanism before release.
Random (probability) sample - A random, or probability, sample is selected through a chance-based design in which every unit in the target population covered by the design has a known...
Random rounding - Random rounding is a statistical disclosure-control technique that replaces a value, often a table count, with a nearby rounding-base value chosen using a...
Random start - A random start is an initial position chosen by a specified random mechanism before a systematic sampling sequence is followed.
Random surfer model - The random surfer model represents movement through a linked network as a probabilistic process.
Random variable - A random variable is a function that assigns a numerical value to each outcome of a random experiment or other probability model.
Randomization, scientific - Scientific randomization uses an explicit chance mechanism to assign experimental units to treatments, determine run order or select units for observation.