https://communities.sas.com/t5/Statistical-Procedures/95-CI-for-ratios/m-p/49531#M2197 what is the correct method and SAS procedure to calculate the 95% confidence interval of the difference of rates in 2 groups? <BR /> <BR /> For example, group A has 28 subjects and 20 improved, group B has 14 subjects and 8 improved. So the improvement rate for group A is 20/28=71.4%, improvement rate for group B is 8/14=57.1%. The difference of rates is 0.14. what is the right way to calculate 95% CI for that? Sun, 31 Jan 2010 05:32:09 GMT abdullala 2010-01-31T05:32:09Z https://communities.sas.com/t5/Statistical-Procedures/95-CI-for-ratios/m-p/49531#M2197 what is the correct method and SAS procedure to calculate the 95% confidence interval of the difference of rates in 2 groups? <BR /> <BR /> For example, group A has 28 subjects and 20 improved, group B has 14 subjects and 8 improved. So the improvement rate for group A is 20/28=71.4%, improvement rate for group B is 8/14=57.1%. The difference of rates is 0.14. what is the right way to calculate 95% CI for that? Sun, 31 Jan 2010 05:32:09 GMT https://communities.sas.com/t5/Statistical-Procedures/95-CI-for-ratios/m-p/49531#M2197 abdullala 2010-01-31T05:32:09Z https://communities.sas.com/t5/Statistical-Procedures/95-CI-for-ratios/m-p/49532#M2198 Set it up as a 2 x 2 table in PROC FREQ and use the RISKDIFF option:<BR /> <BR /> data a;<BR /> do group='A','B';<BR /> do response='Improved','Unimproved';<BR /> input f @@;<BR /> output;<BR /> end;<BR /> end;<BR /> datalines;<BR /> 20 8<BR /> 8 6<BR /> ;<BR /> proc freq;<BR /> weight f;<BR /> table group*response / riskdiff;<BR /> run; Fri, 05 Feb 2010 21:09:29 GMT https://communities.sas.com/t5/Statistical-Procedures/95-CI-for-ratios/m-p/49532#M2198 StatDave 2010-02-05T21:09:29Z