SkillsLib.ai

Statistical Analysis Guide

Guide statistical analysis from hypothesis to regression modeling with rigor

4.4(51 reviews)
500+ downloads
Updated Nov 2026
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What You Can Do

You can confidently navigate complex statistical analyses by working through structured workflows that match your research question and data type to the right test. The skill guides you through assumption validation, helps you interpret results accurately without common pitfalls, and walks you through regression diagnostics with full transparency about what your findings actually mean.

Features

Test Selection

Match your research question and data characteristics (continuous vs. categorical, paired vs. unpaired) to the appropriate statistical test

Assumption Validation

Check normality, homogeneity of variance, independence, linearity, and other preconditions before running analyses

P-Value & CI Interpretation

Understand what p-values and confidence intervals actually tell you, with clear explanations of common misinterpretations

Effect Size Quantification

Calculate and interpret Cohen's d, Cramér's V, R², and other effect sizes to assess practical significance

Regression Diagnostics

Evaluate model fit, identify violations, and interpret coefficients, residuals, and multicollinearity

Hypothesis Formulation

Structure your research question as testable hypotheses with appropriate null and alternative statements

Methodological Error Detection

Flag p-hacking, multiple comparison problems, and other common analytical mistakes

Worked Examples

Apply analyses to realistic datasets with step-by-step interpretation and visualization guidance

Example Output

Example 1: Selecting a Test

Input: "I have baseline and 6-month follow-up cholesterol levels for 45 patients. Want to know if there's a significant change."

Output:

  • ✓ Use: Paired t-test (same subjects, two time points)
  • Check assumption: Are differences approximately normally distributed? (Q-Q plot or Shapiro-Wilk test)
  • Expected output: t-statistic, degrees of freedom, p-value, 95% CI for mean difference, Cohen's d
  • Interpretation: p < 0.05 suggests evidence of change; report the CI and effect size together

Example 2: Regression Diagnostics

Input: "Built a model predicting sales from marketing spend and competitor pricing. R² = 0.62. Are residuals okay?"

Output:

  • ✓ Plot residuals vs. fitted values → check for homoscedasticity
  • ✓ Q-Q plot of residuals → check normality
  • ✓ Check VIF for each predictor → multicollinearity screening
  • ✓ Report: Adjusted R², RMSE, coefficient 95% CIs, diagnostics interpretation
  • Flag: If R² is moderate but residuals show patterns, consider nonlinear terms or interactions

Example 3: Interpreting Results

Input: "T-test result: t(48) = 2.31, p = 0.024. Cohen's d = 0.45. Significant?"

Output:

  • ✓ Yes, statistically significant at α = 0.05 (p < 0.05)
  • ✓ Effect size is small-to-medium (Cohen's d = 0.45)
  • ✓ 95% CI for difference: [estimate range]
  • ⚠️ Caveat: Statistical significance ≠ practical importance; evaluate effect size in your domain context

What's Included

  • SKILL.md: Complete skill instructions and workflows
  • Test Selection Flowchart: Decision tree for matching research questions to appropriate tests
  • Assumption Checklist: Visual diagnostic checklists for each major test family
  • Interpretation Guide: Plain-language reference for p-values, CIs, effect sizes, and common misinterpretations
  • Regression Diagnostic Checklist: Step-by-step residual analysis and multicollinearity screening protocol

Who It's For

  • Data Scientists — validate model assumptions and report results with statistical rigor
  • Researchers — design hypothesis tests and interpret study results correctly
  • Quality Assurance Engineers — analyze A/B tests and process improvement experiments
  • Epidemiologists & Clinical Trial Analysts — conduct and interpret medical research with proper caveats
  • Product Managers & Analysts — make evidence-based decisions from test results with accurate confidence intervals

Best For

  • Hypothesis testing workflow design (t-tests, ANOVA, chi-square, correlation)
  • Assumption validation before statistical tests
  • P-value and confidence interval interpretation
  • Regression model diagnostics and validation
  • Effect size calculation and practical significance assessment
  • Avoiding common statistical errors and misinterpretations
  • Explaining statistical findings to non-technical stakeholders

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