Sample Proportion Calculator

This calculator tests whether or not a sample proportion is significantly different than a hypothesized proportion.
To conduct the test, simply fill in the values below and then click the “Calculate” button.

Z-statistic: -0.30861

Two-tailed P-value: 0.75762


The formula to find the Z-statistic of the test is as follows:
Z-statistic = (p – pnull) / √[ pnull(1-pnull)/n ]
  • p is the sample proportion
  • pnull is the null hypothesis proportion
  • n is the sample size
Based on the numbers entered above, the Z-statistic is calculated as:
Z-statistic = (.28 – .30) / √[ .30(1-.30)/50) ] = -0.30861

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