longpower-package: Sample size calculations for longitudinal data

Description Details Author(s) References See Also


The longpower package contains functions for computing power and sample size for linear models of longitudinal data based on the formula due to Liu and Liang (1997) and Diggle et al (1994). Either formula is expressed in terms of marginal model or Generalized Estimating Equations (GEE) parameters. This package contains functions which translate pilot mixed effect model parameters (e.g. random intercept and/or slope) into marginal model parameters so that the formulas of Diggle et al or Liu and Liang formula can be applied to produce sample size calculations for two sample longitudinal designs assuming known variance. The package also handles the categorical time Mixed Model of Repeated Measures (MMRM) using the formula of Lu, Luo, and Chen (2008)


Package: longpower
Type: Package
Version: 1.0
Date: 2013-05-22
License: GPL (>= 2)
LazyLoad: yes


Michael C. Donohue <[email protected]> Anthony C. Gamst Steven D. Edland


Diggle PJ, Heagerty PJ, Liang K, Zeger SL. (2002) Analysis of longitudinal data. Second Edition. Oxford Statistical Science Series.

Liu, G., & Liang, K. Y. (1997). Sample size calculations for studies with correlated observations. Biometrics, 53(3), 937-47.

Lu, K., Luo, X., & Chen, P.-Y. (2008). Sample size estimation for repeated measures analysis in randomized clinical trials with missing data. International Journal of Biostatistics, 4, (1)

See Also

lmmpower, power.mmrm, power.mmrm.ar1, lmmpower, diggle.linear.power, edland.linear.power, liu.liang.linear.power

longpower documentation built on May 1, 2019, 7:59 p.m.