How to use the two proportion z-test calculator
Test whether two groups have different proportions, such as conversion rates or survey results. Enter proportion in group 1, group 1 size, proportion in group 2, group 2 size in the fields above; the pooled proportion, test statistic z, two-sided p-value are computed instantly and plotted on the chart so you can see how the answer changes.
Common searches this calculator answers include “two proportion z test”, “A/B test significance”, “compare two proportions”, “calculate two proportion z-test”, “find pooled proportion”.
Formula
Variables
- p1 — Proportion in group 1
- n1 — Group 1 size
- p2 — Proportion in group 2
- n2 — Group 2 size
Worked example
With proportion in group 1 = 0.45, group 1 size = 200, proportion in group 2 = 0.3, group 2 size = 220, the calculator gives pooled proportion ≈ 0.3714286; test statistic z ≈ 3.177445; two-sided p-value ≈ 0.1485921 %.
Frequently asked questions
What is the two proportion z-test calculator used for?
Test whether two groups have different proportions, such as conversion rates or survey results. It helps with questions such as “two proportion z test”, “A/B test significance”, “compare two proportions”.
What is the formula for the two proportion z-test calculation?
Pooled proportion = (p1 × n1+p2 × n2) / (n1+n2). Test statistic z = (p1-p2) / √([Pooled proportion] × (1-[Pooled proportion]) × (1 / n1+1 / n2)). Two-sided p-value (%) = 2 × (1-ncdf(abs([Test statistic z]))) × 100. Here p1 is proportion in group 1, n1 is group 1 size, p2 is proportion in group 2, n2 is group 2 size.
What inputs do I need for the two proportion z-test calculator?
You need proportion in group 1, group 1 size, proportion in group 2, group 2 size. Each field is pre-filled with a typical example so you can see how the result responds as you edit the numbers.
How do I use the two proportion z-test calculator?
Type values into the input fields. Results and the chart update instantly. Use Reset to restore the example values, Copy results to paste them elsewhere, or Share to copy a link that preserves your inputs.
Is the two proportion z-test result exact?
Calculations use standard formulas and double-precision arithmetic, then display about seven significant figures. Real-world measurements carry uncertainty, so treat results as estimates unless your inputs are exact.