One-sided test - A one-sided test is a hypothesis test designed to detect a departure in one specified direction.
One-way analysis of variance - One-way analysis of variance is a statistical framework for comparing the means of groups defined by a single factor.
One-way ANOVA - One-way ANOVA is the abbreviated name for one-way analysis of variance: a method for comparing quantitative outcomes across groups defined by one factor.
Open-ended question - An open-ended question invites a respondent to provide an answer in their own words rather than choose only from a predetermined set of response options.
Open-label trial - An open-label trial is an intervention study in which participants and the investigators providing the intervention know which treatment or strategy each...
Opinion poll - An opinion poll is a survey designed to measure people's views, preferences, or intentions on specified questions.
Optimal design - Optimal design is an approach to selecting experimental runs by optimizing a stated statistical criterion under a specified model and practical constraints.
Optimal experimental design - Optimal experimental design is the planning of measurements, treatment assignments, or experimental settings to optimize a defined measure of information or...
Order effect - An order effect is a change in responses or performance attributable to the sequence in which conditions, tasks, questions, or treatments are presented.
Order of integration - The order of integration describes how many ordinary differences are needed to remove a time series' stochastic trend and obtain an integrated-of-order-zero...
Order statistic - An order statistic is an observation identified by its position after a sample is sorted from smallest to largest.
Ordinal interaction - An ordinal interaction is an interaction in which a specified group difference changes in magnitude across levels of another variable without reversing...
Ordinal scale - An ordinal scale classifies observations into categories with a meaningful order, without establishing equal distances between adjacent categories.
Orthogonal array - An orthogonal array is a structured table of experimental or test settings with a specified balance property.
Orthogonal array testing - Orthogonal array testing selects software or system test configurations using an orthogonal array: a table in which every combination of levels across any...
Orthogonal contrasts - Orthogonal contrasts are linear comparisons of group means that are uncorrelated under a specified statistical model.
Out of control - Out of control describes a process whose observed behavior signals a departure from the stable variation expected under a statistical control model.
Owen's T function - Owen's T function is a special mathematical function used to calculate certain normal-distribution probabilities.
P-rep - P-rep, usually written p_rep, is a proposed statistic intended to estimate the probability that a replication produces an effect with the same sign as an...
P/T ratio - The P/T ratio, or precision-to-tolerance ratio, compares a stated width of measurement-system variation with the permitted specification width.
P-value - A p-value is a probability calculated under a specified null model: the probability of obtaining a test statistic at least as extreme as the observed value...
Page's trend test - Page's trend test, also called Page's L test, is a rank-based test for a prespecified ordering of responses across treatments or conditions measured within...
Paired data - Paired data consist of observations linked in meaningful pairs, such as two measurements from the same person or results from two methods applied to the...
Paired difference test - A paired difference test evaluates a hypothesis using differences between observations that belong together, such as two measurements on the same person or...
Paradigm (experimental) - An experimental paradigm is a recognizable framework for conducting a type of experiment, including its central task, manipulation, comparison conditions...
Parallel analysis - Parallel analysis is a method for helping choose how many components or factors to retain by comparing observed eigenvalues with corresponding eigenvalues...
Parallelogram model - The parallelogram model is a vector-based approach to analogy: it represents a relation as the difference between two vectors and applies that difference to...
Parametric hypothesis - A parametric hypothesis is a statement about one or more parameters of a probability distribution or statistical model.
Parametric test - A parametric test is a statistical test whose reference distribution or inference is derived from a model with specified distributional or parameter...
Pareto analysis - Pareto analysis ranks categories by their contribution to a defined total, such as number of incidents, cost, or time lost, to help identify priorities for...
Park test - The Park test is a regression-based diagnostic for heteroscedasticity, using an auxiliary relationship between the logarithm of squared residuals and the...
Partial Area Under the ROC Curve - Partial area under the ROC curve, or partial AUC, summarizes a classifier's ranking performance over a specified portion of the receiver operating...
Partial autocorrelation function - The partial autocorrelation function, or PACF, describes the linear association between a time series and its lagged values after accounting for the...
Partial correlation - Partial correlation measures the association between two variables after accounting for their relationships with one or more specified control variables.
Partialing - Partialing, also spelled partialling, is statistically adjusting for one or more variables when examining relationships among other variables.
Partially open question - A partially open question is a survey question that combines structured response options with an opportunity to answer in the respondent's own words.
Pearson correlation coefficient - The Pearson correlation coefficient measures the direction and strength of linear association between two quantitative variables.
Pearson's chi-square ( c 2 ) - Pearson's chi-square is a statistic that compares observed counts with counts expected under a specified null hypothesis.
Per-comparison error rate - The per-comparison error rate is the Type I error probability associated with an individual hypothesis test: rejecting that test's null hypothesis when it...
Per-word entropy - Per-word entropy expresses uncertainty in a word-generating process on an average-per-word basis.
Percentage of agreement - Percentage of agreement is the percentage of comparable observations for which two or more assessments match, under an explicitly stated agreement rule.
Percentile - A percentile is a value marking a specified cumulative position in a distribution. The 75th percentile, for example, corresponds to cumulative probability 0.75.
Permutation test - A permutation test assesses a statistic by comparing its observed value with values produced by rearrangements allowed under a null hypothesis or an...
Permutational analysis of variance - Permutational analysis of variance commonly refers to PERMANOVA, or permutational multivariate analysis of variance.
Permutations - Permutations are ordered arrangements of objects.
Persistent failure model - A persistent failure model represents a fault as a state that continues across time, rather than treating each faulty observation as an unrelated accident.
Phase dispersion minimization - Phase dispersion minimization, usually abbreviated PDM, is a method for finding candidate periods in time-series data.
Phillips - Perron test - The Phillips - Perron test is a time-series test whose null hypothesis is that a series has a unit root.