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: Fri Oct 18, 2019 @ 08:57


 Sample 1  Sample 2 
Sample Proportion 0.5 0.3214
Sample size 28 28
Significance level 0.05
1- or 2-tailed test 2-tailed


 Sample 1   Sample 2  Difference 
Sample proportion 0.5 0.3214 0.1786
95% CI (asymptotic) 0.3148 - 0.6852 0.1484 - 0.4944 -0.0791 - 0.4363
z-value 1.4
P-value 0.1743
Interpretation Not significant,
accept 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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