2-sample z-test to compare sample proportion

Input Values


Compare two sample proportions using the 2-sample z-test. P-values can be calculated for one- or two-tailed comparisons and are compared results to a specified significance level.

Inputs are:

  • sample proportions for each sample;
  • sample sizes for each sample;
  • specified significance level; and
  • whether test is one-tailed or two-tailed.
Outputs include:
  • Difference in sample proportions;
  • Asymptotic (normal approximation) confidence limits (based on specified significance level) for the proportions and their difference; and
  • z and P values for the difference in proportions and their interpretation; and
  • whether or not z * p values are > 5 (to ensure test validity); and
  • a plot of the confidence limits.

Summary data:
  Sample 1 Sample 2
Sample proportion:
Sample size:
Desired significance level:
One-tailed Two-tailed

z-test to compare two proportion

Analysed: Thu Aug 17, 2017 @ 11:40


 Sample 1  Sample 2 
Sample Proportion 0.0419 0.0383
Sample size 135934 128825
Significance level 0.01
1- or 2-tailed test 2-tailed


 Sample 1   Sample 2  Difference 
Sample proportion 0.0419 0.0383 0.0036
99% CI (asymptotic) 0.0405 - 0.0433 0.0369 - 0.0397 0.0016 - 0.0056
z-value 4.7
P-value <0.0001
Interpretation Statistically significant,
reject null hypothesis that
sample proportions are equal
n by pi n * pi >5, test ok

CI plot

Download excel file of results



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