Case Control Study
The Case Control Study calculator analyses cases (with outcome) vs. controls (without outcome) to compute odds ratios for prior exposure.
Step 1 — Choose data source
- Sample Data Download — template Excel file
- Excel Import — upload your own file
Step 2 — Choose analysis mode
| Mode | What it does |
|---|---|
| Single Exposure | One exposure variable |
| Multi Exposure | Multiple exposures — produces forest plot of odds ratios |
Step 3 — Manual entry (alternative)
- Cases Exposed / Total
- Controls Exposed / Total
Step 4 — Calculate
Results panel shows:
- Odds Ratio (OR) with 95% CI
- Exposure proportions in cases and controls
- Strength of association label
- Effect size interpretation
- CI width assessment — precision rating
- Sample size assessment — adequacy and recommendations
- Plain-language interpretation
Step 5 — Multi-Exposure results
- Summary table with all ORs
- Forest Plot comparing exposures
- Interpretation Guide
A UniversalChatBot is available below.
Statistical methods used
Odds Ratio (OR)
OR = (a * d) / (b * c) with Woolf log-scale CI.
Zero-cell handling
Six distinct scenarios handled explicitly (OR reported as 0, Infinity, or undefined with explanation).
Effect size tiers
| OR range | Label |
|---|---|
| 0.9 - 1.11 | No meaningful effect |
| 0.5 - 0.8 or 1.25 - 2.0 | Medium effect |
| < 0.3 or > 3.0 | Very large effect |
Strength of association (log-OR based)
| |ln(OR)| | Strength | |---|---| | < 0.405 | Weak | | 0.405 - 1.099 | Moderate | | 1.099 - 1.609 | Strong | | >= 1.609 | Very strong |
CI precision assessment
ciWidthPercent = (CI_upper - CI_lower) / OR * 100