Contrasts, pairwise comparisons, and margins

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Contrasts, pairwise comparisons, and margins

Contrasts, pairwise comparisons, marginal means and marginal effects let you analyze the relationships between your outcome variable and your covariates, even when that outcome is binary, count, ordinal, categorical, or survival. Compute adjusted predictions with covariates set to interesting or representative values. Or compute marginal means for each level of a categorical covariate. Make comparisons of the adjusted predictions or marginal means using contrasts. After fitting almost any model in Stata, analyze the effect of covariate interactions, and easily create plots to visualize those interactions.

Contrasts

Analysis of main effects, simple effects, interaction effects, partial interaction effects, and nested effects
Comparisons against reference groups, of adjacent levels, or against the grand mean
Orthogonal polynomials
Helmert contrasts
Custom contrasts
ANOVA-style tests
Contrasts of nonlinear responses
Multiple-comparison adjustments
Balanced and unbalanced data
Contrasts in odds-ratio metric
Contrasts of means, intercepts, and slopes
Graphs of contrasts
Interaction plots

Watch Introduction to contrasts in Stata: Oneway ANOVA.

Pairwise comparisons

Compare estimated means, intercepts, and slopes
Compare marginal means, intercepts, and slopes
Balanced and unbalanced data
Nonlinear responses
Multiple-comparison adjustments: Bonferroni, Šidák, Scheffé, Tukey HSD, Duncan, and Student–Newman–Keuls adjustments
Group comparisons that are significant
Graphs of pairwise comparisons

Marginal analysis

Estimated marginal means
Marginal and partial effects
Average marginal and partial effects
Least-squares means
Predictive margins
Adjusted predictions, means, and effects
Works with multiple outcomes simultaneously
Contrasts of margins
Pairwise comparisons of margins
Profile plots
Graphs of margins and marginal effects

Watch Introduction to margins in Stata tutorials

Categorical variables
Continuous variables
Interactions

Watch Profile plots and interaction plots in Stata tutorials

A single categorical variable
A single continuous variable
Interactions of categorical variables
Interactions of categorical and continuous variables
Interactions of two continuous variables

Additional resources

See New in Stata 18 to learn about what was added in Stata 18.

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