Example of 2 Proportions

A university financial aid officer samples undergraduate students to determine whether male or female students are more likely to get a summer job. Of the 802 male students sampled, 725 got a job in the summer, and 573 of 712 female students sampled got a job.

The officer performs a 2 proportions test to determine whether male or female students are more likely to get a job in the summer.

  1. Choose Stat > Basic Statistics > 2 Proportions.
  2. From the drop-down list, select Summarized data.
  3. In Sample 1, enter 725 for Number of events and 802 for Number of trials.
  4. In Sample 2, enter 573 for Number of events and 712 for Number of trials.
  5. Click OK.

Interpret the results

The null hypothesis states that the difference in the proportion of male students and the proportion of female students who get a summer job is 0. Because the p-value is 0.000, which is less than the significance level of 0.05, the financial aid officer rejects the null hypothesis. The results indicate that there is a difference between the proportion of male students who get a summer job and the proportion of female students who get a summer job.

Test and CI for Two Proportions

Method p₁: proportion where Sample 1 = Event p₂: proportion where Sample 2 = Event Difference: p₁ - p₂
Descriptive Statistics Sample N Event Sample p Sample 1 802 725 0.903990 Sample 2 712 573 0.804775
Estimation for Difference 95% CI for Difference Difference 0.0992147 (0.063671, 0.134759) CI based on normal approximation
Test Null hypothesis H₀: p₁ - p₂ = 0 Alternative hypothesis H₁: p₁ - p₂ ≠ 0
Method Z-Value P-Value Normal approximation 5.47 0.000 Fisher's exact 0.000
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