```Date: Tue, 21 Feb 2012 10:46:44 -0600 Reply-To: Robin R High Sender: "SAS(r) Discussion" From: Robin R High Subject: Re: Non-inferiority Study Comments: To: June Gothberg In-Reply-To: <201202201810.q1K5GaO0011052@wasabi.cc.uga.edu> Content-Type: text/plain; charset="US-ASCII" June, A review of this code can help you work through non-inferiority calculations. PROC TTEST works under the concept of equivalence, but the lower bound can also be used for non-inferiority tests (replicated with PROC MIXED). Also, with more than two class levels, PROC MIXED can compute pvalues for non-inferiority directly from the file of LSMEAN differences. DATA vnue; lvl = 'Control' ; do id = 1 to 9; y = 15 + rannor(928234); output; end; lvl = '1 venue' ; do id = 1 to 9; y = 12 + rannor(0); output; end; lvl = '2 venue' ; do id = 1 to 9; y = 11 + rannor(0); output; end; RUN; %let hxL = -3; * the means of ven 1 and ven 2 can be up to 3 units lower than control (need to set this in the context of your data); * change to -4 and observe difference in output; ods exclude equality conflimits; PROC TTEST DATA =vnue dist=normal tost(&hxL., 999); * large upper bound -- not needed for non-inf ; WHERE lvl IN ('Control', '1 venue'); CLASS lvl; VAR y; TITLE ; run; ODS OUTPUT diffs=dfs; ODS SELECT lsmeans covparms tests3; PROC MIXED DATA=vnue ; WHERE lvl IN ('Control', '1 venue'); * remove this WHERE statement and make both comparisons with one run; CLASS lvl; MODEL y = lvl; * if computed 95% lower bound (enter alpha=.10 to get 5% lower interval) is less than your specified non-inferiority limit, then pvalue indicates cannot accept non-inferiority; LSMEANS lvl / diff cl alpha=.10; run; DATA dfs; SET dfs; NonInfLimit = &hxL. ; tupr = (estimate - NonInfLimit )/stderr; pv_upr= 1-probt(abs(tupr),df); * for non-inferiority test; LowerBound = estimate - ABS(tinv(.05,df))*stderr; * shows how to compute lower bound ; run; PROC PRINT DATA=dfs NOObs; WHERE _lvl EQ 'Control'; VAR lvl _lvl LowerBound NonInfLimit lower Estimate StdErr DF tupr pv_upr ; FORMAT t: 6.2 pv: pvalue6.4; run; Robin High UNMC From: June Gothberg To: SAS-L@LISTSERV.UGA.EDU Date: 02/20/2012 12:10 PM Subject: Re: Non-inferiority Study Sent by: "SAS(r) Discussion" Thank you for your reply Robin. I conducted a study using a 3x3 LSD and have two replications of control venue, venue 1, venue 2. So a total of 18 (2 - 3x3) or 9 each. There are more participants, but I am using mean percent as I am measuring at the level of venue. Does this give you enough information? June ```

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