Cohort Study
The Cohort Study calculator analyses exposed vs. unexposed groups followed forward in time to compute relative risk and related epidemiological measures.
Step 1 — Enter your 2x2 table
- Exposed Events / Total
- Unexposed Events / Total
Step 2 — Or upload Excel data
After uploading, an Excel Analysis Mode Selector offers:
| Mode | What it does |
|---|---|
| Single column mapping | One analysis at a time |
| Multi-column mapping | Multiple exposures vs same outcome — generates forest plot |
Step 3 — Calculate
Results panel shows:
- Incidence rates in exposed and unexposed cohorts
- Relative Risk (RR) with 95% CI
- Attributable Risk (AR) with 95% CI
- Population Attributable Risk (PAR) with 95% CI
- Odds Ratio (OR) with 95% CI
- Chi-square statistic with p-value
- Interpretation — direction, significance, public-health impact
Step 4 — Multi-exposure results
When using multi-column analysis:
- All Crosstabs View — every 2x2 table
- Summary Table — all RRs and p-values
- Forest Plot — visual effect size comparison
A UniversalChatBot is available below.
Statistical methods used
Relative Risk (RR)
RR = p_E / p_U with log-scale CI: exp(ln(RR) +/- 1.96 * SE_logRR)
Attributable Risk (AR)
AR = p_E - p_U with Wald SE.
Population Attributable Risk (PAR)
PAR = P_e * (RR - 1) / (P_e * (RR - 1) + 1)
where P_e = exposure prevalence in the population.
Chi-square test
Standard 2x2 test without continuity correction.
Hypothesis statement
- H0: RR = 1 (no association)
- H1: RR != 1
- alpha = 0.05