Power Calculations for Data Missing by Design: Applications to a Follow-Up Study of Lead Exposure and Attention
设计性缺失下的功效计算:铅暴露与注意力随访研究
Longitudinal designs often change at critical times based on available funding, staffing, scientific opportunities, and subjects. This article presents three levels of investigation into missingness by design in a partially completed longitudinal study: Missingness that is completely at random (MCAR), at random (MAR), and nonignorable (MN). We first derive new expressions for the asymptotic variance and power based on multivariate normal data that are either MCAR or missing…