Power analyses for longitudinal study designs with missing data

X. M. Tu, J. Zhang, J. Kowalski, J. Shults, C. Feng, W. Sun, W. Tang

Research output: Contribution to journalArticlepeer-review


Existing methods for power analysis for longitudinal study designs are limited in that they do not adequately address random missing data patterns. Although the pattern of missing data can be assessed during data analysis, it is unknown during the design phase of a study. The random nature of the missing data pattern adds another layer of complexity in addressing missing data for power analysis. In this paper, we model the occurrence of missing data with a two-state, first-order Markov process and integrate the modelling information into the power function to account for random missing data patterns. The Markov model is easily specified to accommodate different anticipated missing data processes. We develop this approach for the two most popular longitudinal models: the generalized estimating equations (GEE) and the linear mixed-effects model under the missing completely at random (MCAR) assumption. For GEE, we also limit our consideration to the working independence correlation model. The proposed methodology is illustrated with numerous examples that are motivated by real study designs.

Original languageEnglish (US)
Pages (from-to)2958-2981
Number of pages24
JournalStatistics in Medicine
Issue number15
StatePublished - Jul 10 2007
Externally publishedYes


  • Asymptotic distribution
  • Generalized estimating equations
  • Linear mixed-effects model
  • Markov process
  • Missing at random

ASJC Scopus subject areas

  • Epidemiology
  • Statistics and Probability


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