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Basic Analysis and Graphing - SAS

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198 Performing Contingency <strong>Analysis</strong> Chapter 6<br />

Two Sample Test for Proportions<br />

Two Sample Test for Proportions<br />

When both the X <strong>and</strong> Y variables have two levels, you can request a two-sample test for proportions. This<br />

test determines whether the chosen response level has equal proportions across the levels of the X variable.<br />

Table 6.10 Description of the Two Sample Test for Proportions Report<br />

Description<br />

Proportion Difference<br />

Lower 95%<br />

Upper 95%<br />

Adjusted Wald Test<br />

Prob<br />

Response <br />

category of interest<br />

Shows the test being performed.<br />

Shows the difference in the proportions between the levels of the X variable.<br />

Shows the lower endpoint of the confidence interval for the difference.<br />

Based on the adjusted Wald confidence interval.<br />

Shows the upper endpoint of the confidence interval for the difference.<br />

Based on the adjusted Wald confidence interval.<br />

Shows two-tailed <strong>and</strong> one-tailed tests.<br />

Shows the p-values for the tests.<br />

Select which response level to use in the test.<br />

Related Information<br />

• “Example of a Two Sample Test for Proportions” on page 210<br />

Measures of Association<br />

You can request several statistics that describe the association between the variables in the contingency table<br />

by selecting the Measures of Association option.<br />

For details about measures of association, see the following references:<br />

• Brown <strong>and</strong> Benedetti (1977)<br />

• Goodman <strong>and</strong> Kruskal (1979)<br />

• Kendall <strong>and</strong> Stuart (1979)<br />

• Snedecor <strong>and</strong> Cochran (1980)<br />

• Somers (1962)<br />

Table 6.11 Description of the Measures of Association Report<br />

Gamma<br />

Based on the number of concordant <strong>and</strong> discordant pairs <strong>and</strong> ignores tied<br />

pairs. Takes values in the range -1 to 1.

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