Statistics — Page 43
Explore statistical methods, their assumptions, interpretation and limitations.
Research field
Method family
Nonlinear VECM
The Nonlinear VECM extends the standard linear VECM by allowing the speed of adjustment toward long-run equilibrium to differ depending on the sign, magnitude, or regime of deviations from that equilibrium. It captures asymmetric or thresho...
Nonlinear WLS
Nonlinear Weighted Least Squares combines the flexibility of nonlinear regression with the variance-stabilizing power of observation-level weights. It minimises a weighted sum of squared residuals around a user-specified nonlinear mean func...
Nonlinear Zivot-Andrews test
The Nonlinear Zivot-Andrews test extends the classical Zivot-Andrews structural-break unit root test by embedding smooth-transition nonlinear adjustment into the test regression. It jointly searches for an endogenous structural break and al...
Nonlinear difference GMM
Nonlinear Difference GMM extends the Arellano-Bond difference GMM estimator to models where the structural relationship between the outcome and its predictors is inherently nonlinear. By first-differencing to eliminate individual fixed effe...
Nonparametric Quantile Regression
Quantile regression, introduced by Koenker and Bassett in 1978, models a chosen conditional quantile (such as the median or the 25th and 75th percentiles) of a continuous outcome rather than its mean. Its nonparametric variants fit these qu...
OLS Regression
Ordinary Least Squares is the classical linear regression method that explains a continuous outcome as a linear combination of predictors. It estimates the coefficients by minimising the sum of squared residuals, and under the Gauss-Markov...
Oaxaca-Blinder Decomposition
The Oaxaca-Blinder decomposition is a regression-based technique that splits the difference in a mean outcome between two groups — classically the average wage gap between men and women or between racial groups — into a part explained by di...
Oaxaca-Blinder Health Decomposition
The Oaxaca-Blinder decomposition partitions the mean difference in a health outcome between two groups into a portion explained by differences in their measured characteristics and a residual, unexplained portion attributed to differences i...
Older People's Quality of Life Questionnaire
The Older People's Quality of Life Questionnaire (OPQOL) is a 35-item multidimensional self-report measure of quality of life developed by Ann Bowling and distinguished by its lay, bottom-up origins. Rather than imposing expert-defined doma...
One-sample t-test
The one-sample t-test is a parametric hypothesis test that determines whether the mean of a single sample differs significantly from a known or hypothesized population value. Derived from Student's (Gosset's) 1908 t-distribution, it assumes...
One-way ANOVA
One-way ANOVA is a parametric hypothesis test that compares the means of three or more independent groups on a single continuous outcome to decide whether at least one group mean differs. It rests on the variance-partitioning framework intr...
Onward Migration Analysis
Onward migration analysis studies what happens after a migrant's first move: rather than settling permanently or returning home, many migrants move again to a third country or region, a secondary or 'onward' move that conventional origin-to...
Optimal Experimental Design
Optimal experimental design is a computer-aided approach to constructing experiments that maximises statistical efficiency for a given model and run budget. Formalised by V. V. Fedorov in 1972, it selects experimental points from a candidat...
Ordered Logit
Ordered logit is a cumulative regression model for an ordinal dependent variable, fitting a logit (or probit) link to the cumulative category probabilities. Developed in McCullagh's 1980 treatment of regression models for ordinal data, it i...
Ordinal CFA
Ordinal confirmatory factor analysis (Ordinal CFA) tests a pre-specified factor structure when the observed indicators are ordinal — typically Likert-type survey items. By using polychoric correlations and robust estimators such as WLSMV, i...
Ordinal Content Validity
Ordinal content validity replaces the traditional binary (yes/no) expert relevance judgment with a graded, Likert-type rating scale, allowing richer expert opinion to be captured when evaluating whether scale items adequately represent the...
Ordinal Convergent Validity
Ordinal convergent validity assesses the degree to which indicators of the same latent construct correlate strongly with each other when those indicators are measured on ordinal (e.g., Likert-type) scales. It adapts standard convergent vali...
Ordinal Cronbach's Alpha
Ordinal Cronbach's alpha is a reliability coefficient computed from polychoric or polyserial correlations rather than Pearson correlations, making it appropriate for Likert-type and other ordinal item response data. It corrects the systemat...
Ordinal Differential Item Functioning
Ordinal differential item functioning analysis detects whether an ordered-category item (such as a Likert-scale question) functions differently across demographic or cultural groups after controlling for the latent trait being measured. It...
Ordinal Discriminant Validity
Ordinal discriminant validity assesses whether a latent construct measured by ordinal (Likert-type) items is empirically distinct from other constructs in the same instrument. It applies polychoric correlations and ordinal-appropriate facto...
Ordinal EFA
Ordinal exploratory factor analysis discovers latent factors underlying a set of ordinal items — typically Likert scales — by computing polychoric correlations among the items and then applying a weighted least squares estimator. It avoids...
Ordinal Generalizability Theory
Ordinal generalizability theory extends classical G-theory to the analysis of reliability and measurement error when item responses are ordered categorical (e.g., Likert-type) rather than continuous. It partitions score variance into compon...
Ordinal IRT
Ordinal item response theory (ordinal IRT) comprises a family of probabilistic models — most notably the Graded Response Model and the Partial Credit Model — that relate a respondent's standing on a latent trait to the probability of choosi...
Ordinal Item Analysis
Ordinal item analysis evaluates each individual item in a rating-scale or Likert-type instrument using descriptive and correlational statistics suited to ordered categorical response formats. It guides item selection and refinement by flagg...