https://communities.sas.com/t5/Statistical-Procedures/Sample-size-calculation-using-Bonferroni-p-value/m-p/25635#M940 I need to calculate sample size for categorical data with three groups.<BR /> Proc Power and Proc GLMpower are using an alpha level of significance of 0.05 by default. I know that I can change it if I wish.<BR /> In our data we adjusted Fisher exact / Chi_square p-value by bonferroni method Now p-value is very small, like 0.0009, for example. Can I use this value as an alpha in Proc power? Are there any other SAS procedures that can calculate sample size using a Bonferroni p-value as a reference?<BR /> <BR /> Thank you very much for the help. Fri, 29 Oct 2010 23:25:26 GMT deleted_user 2010-10-29T23:25:26Z https://communities.sas.com/t5/Statistical-Procedures/Sample-size-calculation-using-Bonferroni-p-value/m-p/25635#M940 I need to calculate sample size for categorical data with three groups.<BR /> Proc Power and Proc GLMpower are using an alpha level of significance of 0.05 by default. I know that I can change it if I wish.<BR /> In our data we adjusted Fisher exact / Chi_square p-value by bonferroni method Now p-value is very small, like 0.0009, for example. Can I use this value as an alpha in Proc power? Are there any other SAS procedures that can calculate sample size using a Bonferroni p-value as a reference?<BR /> <BR /> Thank you very much for the help. Fri, 29 Oct 2010 23:25:26 GMT https://communities.sas.com/t5/Statistical-Procedures/Sample-size-calculation-using-Bonferroni-p-value/m-p/25635#M940 deleted_user 2010-10-29T23:25:26Z https://communities.sas.com/t5/Statistical-Procedures/Sample-size-calculation-using-Bonferroni-p-value/m-p/25636#M941 I think that you have some study re-design to do. A Bonferroni alpha level of 0.0009 indicates that you have 55 tests. A primary hypothesis (at least in a clinical trial) should be designed for just one test and maybe a few interim looks. Mon, 01 Nov 2010 13:08:48 GMT https://communities.sas.com/t5/Statistical-Procedures/Sample-size-calculation-using-Bonferroni-p-value/m-p/25636#M941 Doc_Duke 2010-11-01T13:08:48Z