Example of a Two Sample Test for Proportions

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Basic Analysis • Contingency Analysis • Additional Examples of the Contingency Platform • Example of a Two Sample Test for Proportions

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Example of a Two Sample Test for Proportions

This example uses the Car Poll.jmp sample data table. Examine the probability of being married for males and females.

1.

Select Help > Sample Data Library and open Car Poll.jmp.

2.

Select Analyze > Fit Y by X.

3.

Select marital status and click Y, Response.

4.

Select sex and click X, Factor.

5.

6.

From the red triangle menu next to Contingency Analysis, select Two Sample Test for Proportions.

Figure 6.111 Example of the Two Sample Test for Proportions Report

In this example, you are comparing the probability of being married between females and males. See the Row% in the Contingency Table to obtain the following:

P(Married|Female)=0.6884

P(Married|Male) = 0.6121

The difference between these two numbers, 0.0763, is the Proportion Difference shown in the report. The two-sided confidence interval is [-0.03175, 0.181621]. The p-value by the adjusted Wald method corresponding to the confidence interval is 0.1686, which is close to the p-value (0.1665) by Pearson’s Chi-square test. Generally, Pearson’s Chi-square test is more popular than the modified Wald’s test for testing the difference of two proportions.

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Help created on 7/12/2018