Power for linear models of longitudinal data with applications to Alzheimer’s Disease Phase II study design
نویسندگان
چکیده
We will discuss power and sample size estimation for randomized placebo controlled studies in which the primary inference is based on the interaction of treatment and time in a linear mixed effects model (Laird and Ware, 1982). We will demonstrate how the sample size formulas of (Liu and Liang, 1997) for marginal or model fit by generalized estimating equation (GEE) (Zeger and Liang, 1986) can be adapted for mixed effects models. Finally, using mixed effects model estimates based on data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI), we will give examples of sample size calculations for models with and without baseline covariates which may help explain heterogeneity in cognitive decline and improve power.
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