Can you please help me with sample size calculation of a clustered RCT where the outcome is a rate and there is a baseline rate? That is at the beginning of the study both groups will have an outcome rate of 76/1000 days. We will have 23 clusters in each arm and 104 participants per cluster (SD=33) and expecting to follow-up the groups for 1 years. We need to know the minimum detectable difference for 80% power at 5% level with an ICC of 0.01. I am using the following Stata command but the effect size looks very high. clustersampsi, rates detectabledifference r1(.076) m(37960) k(23) rho(.01) size_cv(.45) alpha(0.05) beta(0.8) base_correl(0)   when I am doing the calculation for a stepped wedged RCT with 3 steps (3 months duration) it is coming much lower. steppedwedge, rates detectabledifference complete(1) vartotal(1) r1(.076) m(9360) k(12) rho(.01) alpha(0.05) beta(0.8) steps(3)   The difference is very high. I want to cross-check this with a SAS program. ... View more

Can you please help me with sample size calculation of a clustered RCT where the outcome is a rate and there is a baseline rate? That is at the beginning of the study both groups will have an outcome rate of 76/1000 days. We will have 23 clusters in each arm and 104 participants per cluster (SD=33) and expecting to follow-up the groups for 1 years. We need to know the minimum detectable difference for 80% power at 5% level with an ICC of 0.01. I am using the following Stata command but the effect size looks very high. clustersampsi, rates detectabledifference r1(.076) m(37960) k(23) rho(.01) size_cv(.45) alpha(0.05) beta(0.8) base_correl(0)   when I am doing the calculation for a stepped wedged RCT with 3 steps (3 months duration) it is coming much lower. steppedwedge, rates detectabledifference complete(1) vartotal(1) r1(.076) m(9360) k(12) rho(.01) alpha(0.05) beta(0.8) steps(3)   The difference is very high. I want to cross-check this with a SAS program.   ... View more

Hi, Can we calculate minimum detectable effect size for a cluster randomise trial(cRCT)? I have the following situation. A two arm cRCT with 20 clusters in each arm, average cluster size is 30 (SD=20). Power=80%, Alpha=0.05. Proportion of outcome in the control group is 65%. What difference in the outcome between the 2 arms I can estimate from this study? Bayzid ... View more

Is there any easy way to calculate sample size for a Poisson model with offset? I am planning a cohort study with recurrence short term outcome. That is, one participant can get the outcome multiple times during the follow-up period. ... View more

I need to fit a poisson model with offset including restricted cubic spline of a continuous covariate. I want to use the effect statement to automatically generate the spline variables at my preferred values. Can you please let me know what procedures can do it? I can see that proc genmod doesn’t allow select statement. ... View more