RTI uses cookies to offer you the best experience online. By clicking “accept” on this website, you opt in and you agree to the use of cookies. If you would like to know more about how RTI uses cookies and how to manage them please view our Privacy Policy here. You can “opt out” or change your mind by visiting: http://optout.aboutads.info/. Click “accept” to agree.
Sizing a trial to alter the trajectory of health behaviours: Methods, parameter estimates, and their application
Murray, DM., Blitstein, J., Hannan, PJ., Baker, WL., & Lytle, LA. (2007). Sizing a trial to alter the trajectory of health behaviours: Methods, parameter estimates, and their application. Statistics in Medicine, 26(11), 2297-2316. https://doi.org/10.1002/sim.2714
Group-randomized trials often involve repeat observations on the same participants. When there are no more than two observations from each participant, standard mixed-model regression methods for a pretest-posttest design can be used. When there are more than two observations from each participant, random coefficients models may be useful. This paper describes the random coefficients analysis appropriate to data from an extended nested cohort design and presents the methods for power analysis and sample size calculations based on that analysis. We provide estimates for the parameters required for those calculations for a number of adolescent health behaviours. We also show how the estimates can be used to plan a future trial. Copyright (C) 2006 John Wiley & Sons, Ltd