topic Power calculation for proportions in Statistical Procedures https://communities.sas.com/t5/Statistical-Procedures/Power-calculation-for-proportions/m-p/50180#M2222 Hello,<BR /> <BR /> I want to ask why the following code is not working:<BR /> <BR /> proc power;<BR /> TwoSampleFreq <BR /> test =pchi <BR /> groupproportions =(1 0.80) <BR /> nullproportiondiff =0 <BR /> NPerGroup =20<BR /> SIDES =1 <BR /> POWER =.<BR /> Alpha =0.05;<BR /> run;<BR /> <BR /> invalid input<BR /> WARNING: The magnitude of the effect is ill-defined in one of the scenarios in the output table.<BR /> <BR /> I think that it's due to my assumption that 100% of the patients in the placebo group develop the disease. Is it too strong? <BR /> Thanks in advance,<BR /> Best regards,<BR /> Cyril Mon, 01 Feb 2010 16:41:09 GMT Cyril_FR 2010-02-01T16:41:09Z Power calculation for proportions https://communities.sas.com/t5/Statistical-Procedures/Power-calculation-for-proportions/m-p/50180#M2222 Hello,<BR /> <BR /> I want to ask why the following code is not working:<BR /> <BR /> proc power;<BR /> TwoSampleFreq <BR /> test =pchi <BR /> groupproportions =(1 0.80) <BR /> nullproportiondiff =0 <BR /> NPerGroup =20<BR /> SIDES =1 <BR /> POWER =.<BR /> Alpha =0.05;<BR /> run;<BR /> <BR /> invalid input<BR /> WARNING: The magnitude of the effect is ill-defined in one of the scenarios in the output table.<BR /> <BR /> I think that it's due to my assumption that 100% of the patients in the placebo group develop the disease. Is it too strong? <BR /> Thanks in advance,<BR /> Best regards,<BR /> Cyril Mon, 01 Feb 2010 16:41:09 GMT https://communities.sas.com/t5/Statistical-Procedures/Power-calculation-for-proportions/m-p/50180#M2222 Cyril_FR 2010-02-01T16:41:09Z Re: Power calculation for proportions https://communities.sas.com/t5/Statistical-Procedures/Power-calculation-for-proportions/m-p/50181#M2223 You got it. Underlying any experimental design is the concept that there will be some variability in the process. If you are requiring a 100% effect (or 0%) in one group, then you have no variability in that group. Mon, 01 Feb 2010 21:09:07 GMT https://communities.sas.com/t5/Statistical-Procedures/Power-calculation-for-proportions/m-p/50181#M2223 Doc_Duke 2010-02-01T21:09:07Z Re: Power calculation for proportions https://communities.sas.com/t5/Statistical-Procedures/Power-calculation-for-proportions/m-p/50182#M2224 Thanks DOC Tue, 02 Feb 2010 10:55:16 GMT https://communities.sas.com/t5/Statistical-Procedures/Power-calculation-for-proportions/m-p/50182#M2224 Cyril_FR 2010-02-02T10:55:16Z