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FlorianM
Fluorite | Level 6

Hello,

I have a binary variable (yes/no) and two measuring time (T1 and T2). Thus data are not independant.

I would like to calculate the difference (in percentage) between the proportion of "yes" at T1 and the proportion of "yes" at T2. Moreover i need to calculate the confidence interval of this difference.

I thought it was possible using proc freq (as paired ttest) but i wasn't successufll at getting it to work.

Hoping that you can help me.

Thank you.

 

 

1 ACCEPTED SOLUTION
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FlorianM
Fluorite | Level 6

Thanks a lot for your response.

FreelanceReinh
Jade | Level 19

Later readers of this thread should note:

 

The blog article linked in the accepted solution is about proportions in independent samples. The confidence intervals for a proportion difference in that situation will tend to be too narrow when applied to dependent (paired) samples.

 

A discussion of CIs for the latter situation (including SAS code) can be found in the SESUG 2013 paper SAS® Macros CORR_P and TANGO: Interval Estimation for the Difference between Correlated Proportions ....

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