check_assumptions
Check data or fitted models for violations of normality, homoscedasticity, independence, outliers, and multicollinearity before parametric tests. Get diagnostic tests and plots to confirm assumptions.
Instructions
Check the assumptions behind parametric tests. On raw data: normality (Shapiro-Wilk, Kolmogorov-Smirnov, skew/kurtosis), homogeneity of variance across a group (Levene, Bartlett), outliers (z-scores and Tukey fences) and highly correlated variable pairs, plus Q-Q plots. On a fitted model (pass model instead of variables): residual normality, Breusch-Pagan heteroscedasticity, Durbin-Watson independence, VIF, and the standard four-panel diagnostic plot.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| data | No | Dataset name; omit when checking a model. | |
| group | No | Grouping column - enables per-group normality and variance homogeneity tests. | |
| model | No | Name of a fitted model in the session; checks residual assumptions instead. | |
| plots | No | Include diagnostic plots. | |
| z_cut | No | Absolute z-score above which a value counts as an outlier. | |
| checks | No | Subset of: normality, homogeneity, outliers, multicollinearity, independence. | |
| digits | No | Decimal places. | |
| variables | No | Numeric columns to check (default: all numeric). |