| name | vera-stat-binary-testing |
| description | Runs class balance diagnostics and primary association tests for binary outcome variables (0/1, yes/no, survived/died, pass/fail). Produces proportion tables, class balance check with rare-event warning, descriptives by outcome level, chi-square test of independence with Cramer's V, Fisher's exact test when cell counts are small, odds ratio with 95% CI, and a mosaic or grouped bar chart. Outputs .R and .py scripts with 2 publication-quality plots. Triggered when user has a binary/dichotomous outcome and says "binary outcome," "logistic," "survived or died," "yes or no," "pass or fail," "0/1," "classification," "binary DV," or names a binary variable like survived, admitted, defaulted, churned, diagnosed. Does not handle continuous, count, survival time, ordinal, repeated measures, or SEM. |
| user-invocable | true |
| allowed-tools | Read, Bash, Write, Edit |
Binary Outcome --- Class Balance Diagnostics & Association Testing
Open-source skill.
Workflow
Read each step file in workflow/ before executing that step.
| Step | File | Executor | Output |
|---|
| Collect | workflow/01-collect-inputs.md | Main Agent | Structured input summary |
| Diagnose | workflow/02-check-distribution.md | Main Agent | PART 1 code block |
| Test | workflow/03-run-primary-test.md | Main Agent | PART 2-3 code blocks |
Decision Tree
1. CHECK CLASS BALANCE
├── Balanced (minority ≥ 10%) → standard tests
└── Imbalanced (minority < 10%) → rare event warning, note power limits
2. PRIMARY ASSOCIATION TEST
├── All cells ≥ 5 → Chi-square + Cramer's V + OR
└── Any cell < 5 → Fisher's exact + OR
Required Inputs
| Role | What to collect |
|---|
| Outcome (Y) | Variable name, what 0/1 represents |
| Primary group variable | What defines groups, how many levels |
| Predictors | For recommendation block (not executed) |
| Covariates | For recommendation block (not executed) |
Code Structure
PART 0: Setup & Data Loading
PART 1: Class Balance Diagnostics → plot_01_class_balance.png
PART 2: Primary Association Test → plot_02_mosaic_[var].png
PART 3: Recommendation Block → text listing additional analyses available
Reporting Standards
- p-values: "< .001" not "0.000"; exact to 3 decimals otherwise
- Effect sizes: Cramer's V (chi-square), odds ratio with 95% CI
- Odds ratios: always as "OR = X.XX, 95% CI [X.XX, X.XX]"
- Proportions: report as percentages with 1 decimal
- Chi-square: chi-sq(df) = X.XX, p = .XXX, Cramer's V = .XXX
- Degrees of freedom: always with chi-square statistic
- Sample size: final analytic N
- Decimal places: 1 for proportions, 2 for OR, 3 for p and effect sizes
- Non-significance: "not statistically significant at alpha = .05" --- never "no association"
Association Tests
| Scenario | Expected cells all >= 5 | Any expected cell < 5 |
|---|
| 2x2 or 2xK | Chi-square + Cramer's V | Fisher's exact test |
Paired/matched binary designs -> vera-stat-repeated-testing (handles within-subject comparisons including paired binary data via McNemar's test).
Example Dataset
R built-in Titanic (convert to data frame): outcome = Survived (0/1), predictors = Class, Sex, Age.
Python: sm.datasets.get_rdataset("Titanic").data or reconstruct from counts (offline fallback uses base R Titanic dataset).
Cross-Skill Interface
Output:
├── code_r → .R script
├── code_python → .py script
├── figures/ → 2 PNGs (class balance + mosaic/grouped bar)
└── recommendations → text block (additional analyses available)
