title: LIFESPAN: A tool for the computer-aided design of longitudinal studies.
abstract: Researchers planning a longitudinal study typically search, more or less informally, a multivariate space of possible study designs that include dimensions such as the hypothesized true variance in change, indicator reliability, the number and spacing of measurement occasions, total study time, and sample size. The main search goal is to select a research design that best addresses the guiding questions and hypotheses of the planned study while heeding applicable external conditions and constraints, including time, money, feasibility, and ethical considerations. Because longitudinal study selection ultimately requires optimization under constraints, it is amenable to the general operating principles of optimization in computer-aided design. Based on power equivalence theory (MacCallum et al., 2010; von Oertzen, 2010), we propose a computational framework to promote more systematic searches within the study design space. Starting with an initial design, the proposed framework generates a set of alternative models with equal statistical power to detect hypothesized effects, and delineates trade-off relations among relevant parameters, such as total study time and the number of measurement occasions. We present LIFESPAN (Longitudinal Interactive Front End Study Planner), which implements this framework. LIFESPAN boosts the efficiency, breadth, and precision of the search for optimal longitudinal designs. Its initial version, which is freely available at http://www.brandmaier.de/lifespan, is geared toward the power to detect variance in change as specified in a linear latent growth curve model.
authors: Center for Lifespan Psychology, Max Planck Institute for Human Development Berlin, Germany.
authors: Andreas M
authors: AM
authors: Brandmaier
authors: Department of Psychology, University of Virginia Charlottesville, VA, USA.
authors: Timo
authors: T
authors: von Oertzen
authors: Faculty of Psychology and Educational Sciences, University of Geneva Geneva, Switzerland ; Distance Learning University Switzerland Brig, Switzerland.
authors: Paolo
authors: P
authors: Ghisletta
authors: Adult Cognition Lab, School of Psychology, Georgia Institute of Technology Atlanta, GA, USA.
authors: Christopher
authors: C
authors: Hertzog
authors: Center for Lifespan Psychology, Max Planck Institute for Human Development Berlin, Germany ; Max Planck University College London Centre for Computational Psychiatry and Ageing Research London, UK.
authors: Ulman
authors: U
authors: Lindenberger
keywords: effective error; latent growth curve modeling; optimal design; power equivalence theory; statistical power; structural equation modeling