Dear Community,
I need to calculate the sample size (number of clusters and average number of observations per cluster) needed for a hierarchical 2x2 full factorial trial. Trial centers will be randomized to the four conditions (base, base+A, base+B, base+A+B). In each center, the primary outcome (metric, may be skewed) will be measured for multiple individuals. The effect of A and the effect of B on the outcome as well as their interaction will be of interest.
I intend to use a mixed linear effects model if the distribution of residuals permits (I hope that I will not have to resort to a generalized model or another alternative, there is a chance though I suppose). I will make assumptions on ICC (expected to be rather low, somwhere between 0.02 and 0.04) and cluster size variation. Alpha=0.05, power=0.8.
I am familiar with power calculation for cluster-randomized trials with a hierarchical data structure that are analyzed by a mixed linear effects model where a single treatment effect is of interest, but not for factorial trials. I am also familiar to a limited degree with power calculation for 2x2 full factorial trials, but not with hierarchical data structure.
Your help is greatly appreciated!
Marco
I need to calculate the sample size (number of clusters and average number of observations per cluster) needed for a hierarchical 2x2 full factorial trial. Trial centers will be randomized to the four conditions (base, base+A, base+B, base+A+B). In each center, the primary outcome (metric, may be skewed) will be measured for multiple individuals. The effect of A and the effect of B on the outcome as well as their interaction will be of interest.
I intend to use a mixed linear effects model if the distribution of residuals permits (I hope that I will not have to resort to a generalized model or another alternative, there is a chance though I suppose). I will make assumptions on ICC (expected to be rather low, somwhere between 0.02 and 0.04) and cluster size variation. Alpha=0.05, power=0.8.
I am familiar with power calculation for cluster-randomized trials with a hierarchical data structure that are analyzed by a mixed linear effects model where a single treatment effect is of interest, but not for factorial trials. I am also familiar to a limited degree with power calculation for 2x2 full factorial trials, but not with hierarchical data structure.
Your help is greatly appreciated!
Marco