Randomized blocks design - A randomized blocks design groups experimental units into blocks that are similar on an important source of variation, then randomizes treatments within...
Randomized non-comparative trial - A randomized non-comparative trial assigns participants randomly to two or more arms but evaluates each arm separately rather than making a prespecified...
Randomness test - A randomness test is a statistical procedure that looks for particular departures from a specified random-process model.
Range restrictions - Range restrictions occur when the observations available for analysis cover only a limited part of the variation present in the population of interest.
Rank test - A rank test is a statistical test whose statistic uses the relative ordering of observations, or related ranked quantities, rather than relying directly on...
Ranked data - Ranked data are observations represented by their positions in an ordering rather than by their original numerical values.
Rankrandomization tests - Rank-randomization tests are nonparametric procedures that evaluate a statistic based on ranks against a distribution generated by permitted random...
Rare events - Rare events are outcomes with low probability or low frequency relative to a specified population, exposure or time horizon.
Rasch model - The Rasch model is a probabilistic measurement model relating a person's position on a latent trait to the difficulty of an item.
Rashomon effect in machine learning - The Rashomon effect in machine learning is the presence of multiple different models that predict the same data similarly well.
Ratio estimation - Ratio estimation uses a relationship between a study variable and an auxiliary variable to estimate a population quantity.
Ratio scale - A ratio scale is a measurement scale with meaningful equal intervals and a meaningful zero, so ratios of values can represent ratios of the measured quantity.
Rational subgroups - Rational subgroups are deliberately formed groups of observations used in statistical process control so that within-subgroup variation represents a...
Realized variance - Realized variance is an ex-post measure of variation calculated by summing squared returns over subintervals within a specified period.
Recall bias - Recall bias is systematic error arising when people inaccurately or incompletely remember and report past events or experiences.
Rectified Gaussian distribution - In the clipped-normal sense used here, a rectified Gaussian distribution is the distribution of Y = max(0, X) when X is Gaussian.
Recurrent event analysis - Recurrent event analysis studies events that can occur more than once for the same observational unit over time.
Recursive partitioning - Recursive partitioning builds a model by repeatedly dividing a dataset or predictor space into smaller regions.
Reference class problem - The reference class problem is the difficulty of deciding which group of comparable cases should inform a probability judgment about a particular case.
Reference group - A reference group is a group of observations, or a defined group that could be observed, used as a point of comparison in a study.
Regression Analysis - Regression analysis is a family of statistical methods for studying how an outcome is related to one or more predictors.
Regression coefficients - Regression coefficients are numerical parameters that determine how predictors enter a regression model.
Regression equation - A regression equation is a mathematical expression describing how an outcome, or a chosen conditional summary of that outcome, depends on predictors in a...
Regression line - A regression line is a straight-line representation of a modeled relationship between a numerical outcome and a predictor.
Regression model - A regression model represents a relationship between predictors and an outcome, commonly for predicting a numerical quantity or describing a conditional...
Regression spline - A regression spline models a relationship using polynomial pieces joined at specified locations called knots.
Regression surface - A regression surface represents a fitted relationship between an outcome and two or more predictors.
Regression to the mean - Regression to the mean is the tendency for observations selected because they are unusually high or low to be followed, on average, by less extreme...
Regression tree - A regression tree is a tree-structured predictive model for a numerical outcome.
Rejection region - A rejection region is the set of possible test-statistic values or sample outcomes that lead a specified hypothesis test to reject its null hypothesis.
Relational model - The relational model is a way of representing data as relations, commonly understood as tables with named attributes and records.
Relative frequency view - The relative frequency view interprets probability through the proportion of times an event occurs in repeated trials under specified, stable conditions.
Relative standard error - Relative standard error, usually abbreviated RSE, expresses an estimate's standard error relative to the magnitude of that estimate, commonly as a percentage.
Rendering model - A rendering model describes how a scene and viewing conditions produce an image.
Repeatability - Repeatability is the closeness of agreement among repeated measurement results obtained under the same specified measurement conditions.
Repeated measures design - A repeated measures design obtains multiple observations from the same experimental units or participants, often across time or under several conditions.
Repeated survey - A repeated survey is a sample survey conducted on more than one occasion using essentially the same questionnaire or schedule.
Repeatedmeasures designs - Repeated-measures designs collect several responses from each unit, such as measurements of the same participant across conditions or observations of the...
Replicate - To replicate is to repeat an experiment or study so that its result can be examined again.
Replication (statistics) - Replication in statistics is the repetition of experimental conditions across appropriate units or runs to obtain information about variability and effects.
Research hypothesis - A research hypothesis is a specific, testable proposition about a population, relationship or effect that a study is designed to investigate.
Resentful demoralization - Resentful demoralization is a possible reaction in an experiment or intervention study in which participants who perceive their assigned condition as less...
Residence time (statistics) - In the statistical sense used here, residence time is the expected duration before a stochastic process first reaches or exits a specified boundary...
Residual variance - Residual variance describes variation remaining around a model's fitted values.
Resistance - Resistance is the degree to which a statistical estimate is insensitive to a small number of unusual or substantially changed observations.
Respondent error - Respondent error is a component of survey measurement error arising when a respondent gives an incorrect answer, deliberately or inadvertently.
Response modeling methodology - Response modeling methodology, abbreviated RMM, is a named empirical modeling framework developed by Haim Shore for representing systematic response...
Response surface model - A response surface model is a mathematical approximation describing how a response changes with two or more input factors over a specified region.