Restricted mean survival time - Restricted mean survival time, or RMST, is the expected time spent event-free up to a specified time horizon tau.
Restricted randomization - Restricted randomization is random assignment carried out within predefined constraints rather than over every otherwise possible allocation.
Retrospective study - A retrospective study investigates events or information that already existed when the study was designed or initiated.
Ridge regression - Ridge regression is linear regression fitted with a penalty on the sum of squared coefficient values.
Robust Bayesian analysis - Robust Bayesian analysis studies how Bayesian conclusions change when uncertain modeling inputs are varied.
Robust methods - Robust methods are statistical procedures designed to retain useful performance when specified ideal assumptions are not exactly satisfied.
Root mean square - Root mean square, usually abbreviated RMS, is the square root of the average of squared values.
Root-mean-square deviation - Root-mean-square deviation, or RMSD, is the square root of the average squared difference between matched values and a specified reference.
Root Mean Squared Error - Root Mean Squared Error, abbreviated RMSE, is the square root of the average squared difference between predictions and observed reference values.
Rotation bias - Rotation bias is a systematic difference in survey estimates associated with how long sampled units have participated in a rotating panel or with their...
Rotational invariance - Rotational invariance is the property of a function, representation, or prediction remaining unchanged under specified rotations of its input.
Round-robin test - A round-robin test is an interlaboratory study in which several participants independently perform measurements, analyses, or a defined process under an...
Rubin causal model - The Rubin causal model is a framework for defining and studying causal effects using potential outcomes: the outcomes a unit would have under different...
Ryan procedure (REGWQ) - The Ryan procedure (REGWQ), more fully the Ryan - Einot - Gabriel - Welsch Q procedure, is a stepwise multiple-comparison method for investigating...
S chart - An S chart is a statistical process control chart that plots the sample standard deviation within successive subgroups.
Sample - A sample is a collection of units or observations selected from a population or generated by a specified data-collection process.
Sample augmentation - Sample augmentation, in survey statistics, means maintaining and adding units to an existing sample so that it continues to cover the evolving population...
Sample complexity - Sample complexity describes how many observations a learning or estimation procedure needs to meet a specified performance criterion under stated assumptions.
Sample frame - A sample frame, more commonly called a sampling frame, is the list, map, register, or other operational device used to identify and access units for sample...
Sample mean - The sample mean is the arithmetic average of the observed values of a numeric variable.
Sample ratio mismatch - Sample ratio mismatch, abbreviated SRM, is a statistically significant discrepancy between the observed numbers of experimental units in treatment groups...
Sample rotation - Sample rotation is the planned replacement of some or all units in a recurring survey sample after a specified period of participation.
Sample size - Sample size is the number of units or observations included in a defined sample, usually denoted n.
Sample size determination - Sample size determination is the process of choosing how many units or observations a study needs to meet a defined objective under stated assumptions.
Sample size disparity - Sample size disparity is a difference in the number of available observations across groups.
Sample space - A sample space is the set of all possible outcomes represented by a probability model for an experiment or random process. It is commonly denoted S or Omega.
Sample statistics - Sample statistics are quantities calculated from observed sample data, such as a mean, median, proportion, variance, or correlation.
Sample unique - A sample unique is a record whose combination of specified key-variable values occurs only once within a dataset.
Sample variance - Sample variance is a measure of how widely observations are dispersed around their sample mean.
Sample weighting - Sample weighting assigns different numerical contributions to observations when calculating estimates, fitting models, or evaluating performance.
Sampling design - Sampling design is the set of rules specifying how units are selected from a population or sampling frame.
Sampling distribution - A sampling distribution is the probability distribution of a statistic across the samples that could arise from a specified population and sampling process.
Sampling distribution of differences between means - The sampling distribution of differences between means is the probability distribution of a difference between sample averages over repeated samples drawn...
Sampling distribution of the mean - The sampling distribution of the mean is the probability distribution of the averages produced by repeated samples under a specified population model and...
Sampling error - Sampling error is the random variation in an estimate that arises because information is collected from a sample rather than the entire target population.
Sampling fraction - The sampling fraction is the proportion of a defined finite population selected into a sample, commonly written f = n/N, where n is the sample size and N is...
Sampling probability - Sampling probability, in finite-population sampling, usually means a unit's inclusion probability: the probability that it appears in the sample under the...
Sampling risk - Sampling risk is the possibility that a conclusion based on a sample differs from the conclusion obtained by applying the same examination procedure to the...
Satellite image time series - A satellite image time series is a sequence of satellite observations of an area, ordered by acquisition time and prepared so that measurements can be...
Satterthwaite solution - The Satterthwaite solution is an approximation used to assign effective degrees of freedom when an estimated variance combines contributions with different...
Saturated array - A saturated array, in experimental design, is an orthogonal array whose factor main effects use all the available degrees of freedom after allowing for the...
Saturated model - A saturated model has enough free parameters to reproduce all the independently variable features of the observed data being modeled.
Scale analysis (statistics) - Scale analysis is the examination of questionnaire or test items to determine how they can support measurement of an underlying construct.
Scales of measurement - Scales of measurement describe the relationships represented by values assigned to observations.
Scatterplot smoothing - Scatterplot smoothing estimates a curve through paired observations to describe how a response tends to vary with a predictor.