<7> Let's use an example. data pilot; input Drug1 $ Drug2 $ post1 post2 @@; label Drug1='Drug Period 1' Drug2='Drug Period 2' post1='FeNO period 1' post2='FeNO period 2'; datalines; R T 24 15 T R 15 27 R T 28 23 T R 30 28 T R 6 12 R T 32 22 T R 23 19 R T 32 17 T R 76 41 R T 15 10 T R 20 25 R T 14 15 T R 21 18 R T 66 25 T R 25 42 R T 38 35 R T 20 19 T R 21 19 R T 27 51 T R 24 72 R T 14 14 R T 22 24 T R 22 24 R T 28 36 T R 22 37 T R 27 51 R T 20 22 T R 28 73 R T 44 29 T R 52 23 T R 18 19 R T 29 34 T R 33 45 R T 63 42 T R 27 58 R T 29 30 R T 19 19 T R 29 32 R T 35 22 T R 26 52 ; run; proc ttest data=pilot dist=lognormal; var post1 post2 / crossover= (drug1 drug2); run; /* Geometric mean for treatment ratio = 1.2347 and CV = 0.2224 */ /* Calculate treatment ratio */ data pilot1; set pilot; label post_trt1='FeNO T' post_trt2='FeNO R' post_ratio_drug1_drug2='FeNO R/T'; if drug1='T' then post_trt1=post1; else post_trt1=post2; if drug1='R' then post_trt2=post1; else post_trt2=post2; post_ratio_drug1_drug2=post_trt2/post_trt1; run; proc ttest data=pilot1 dist=lognormal; var post_ratio_drug1_drug2; run; /* Geometric mean = 1.2347 and CV = 0.4590 */ The geometric mean is the same but CV is different. Which CV should I use in proc power? proc power; pairedmeans test=ratio DIST=logNormal meanratio = CV = corr = npairs = . alpha = 0.05 power = 0.9; run; Thanks in advance Favola
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