OPTITXS.r

Program, documents and manuscripts for sample size and power calculation for longitudinal studies written by Xavier Basagaña and Donna Spiegelman

Calculating the minimum number of participants (N) for a fixed number of measurements (r), given pre-specified power; the minimum number of repeated measurements (r) for fixed N, power, and pre-specified study length or time between visits; power for a given (N,r); and the optimal (N,r) subject to power or cost constraints. Compound symmetry, damped exponential, and random slopes covariances are supported.

• optitxs.r: Version 1.1
• optitxs: User Manual

Manuscripts:

• The Design of Observational Longitudinal Studies • Appendix
• Power & sample size calculations for Longitudinal Studies Estimating a Main Effect of a Time-Varying Exposure • Appendix
  
• Power & sample size calculations for Longitudinal Studies Comparing Rates of Change with a Time-Varying Exposure • Appendix