Z-Test Calculator for 2 Population Proportions
This calculator performs a Z-test to compare the proportions of two independent populations or groups.
When to Use
Use the Z-test for proportions when you want to compare the proportion of successes in two independent groups (e.g., proportion of patients responding to treatment in two different drug groups).
Requirements
- Two independent samples
- Binary outcome (success/failure)
- Sufficient sample size (typically np > 5 and n(1-p) > 5 for both groups)
Null Hypothesis
H₀: p₁ = p₂ (the two population proportions are equal)
Formula
Z = (p₁ - p₂) / SE
where SE = √[p̂(1-p̂)(1/n₁ + 1/n₂)]
and p̂ = (x₁ + x₂) / (n₁ + n₂)
