Methods: Mind the Gap

Webinar Series

Power Analyses to Plan Idiographic Clinical Trials, Illustrated for Prevention and Rare Diseases

May 4, 2023
Ty Ridenour
Ty Ridenour, Ph.D., M.A.

RTI International

Stephen Tueller
Stephen Tueller, Ph.D., M.S.

RTI International

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About the Webinar

Within-subject clinical trials have long been considered an inferior option to randomized clinical trials in psychology and medicine even though they can address critical research questions that randomized trials cannot. Coupling within-subject experimental designs with rigorous statistical analysis, referred to as idiographic clinical trials, overcomes many historical limitations of within-subject designs. This has led to recent fundamental advances and spurred a resurgence in using these methods. This presentation briefly reviews idiographic clinical trials, their strengths and limitations, and recent advances in these methodologies. Finally, the newly developed PersonAlyticsPower R package for a priori power analyses to plan study designs is presented. PersonAlyticsPower is illustrated with results from a recent series of Monte Carlo simulations which explored the impact of multiple study design factors on statistical power to detect treatment effects such as sample size, number of repeated observations, and number of observations per study phase. The motivating contexts and examples to illustrate idiographic clinical trials are prevention science and treatments for rare diseases. General recommendations for designing idiographic clinical trials are drawn from the Monte Carlo simulations. This research was supported by funding from the National Center for Advancing Translational Sciences (R21TR002402, principal investigator Ridenour).  

About Ty Ridenour

Dr. Ty Ridenour is a Senior Developmental Behavioral Epidemiologist in the Center on Social Determinants, Risk Behaviors, and Prevention Science at RTI International. Dr. Ridenour has collaborated on idiographic clinical trials research for over 15 years in a range of fields including prevention science, endocrinology, intimate partner violence, psychotherapy, physical rehabilitation, and wearable biosensors. He also has taught graduate courses on idiographic clinical trials and leads development of the PersonAlytics software, funded by the National Center for Advancing Translational Sciences. His content areas of interest are in the etiology and prevention of substance use disorders, unsafe sexual behaviors, and conduct problems.  

About Stephen Tueller

Dr. Stephen Tueller is a Senior Research Statistician in the Division of Applied Justice Research at RTI International. Dr. Tueller provides design and analysis leadership for several ongoing multisite randomized trials, hybrid trials, idiographic clinical trials, and implementation studies in research areas spanning child welfare, juvenile justice, human trafficking, rare diseases, HIV services, adult criminal justice, and addiction. Current projects are funded by the Administration for Children and Families, the National Institutes of Health, National Institutes of Justice, and Arnold Ventures. Dr. Tueller’s current methodological work focuses on developing statistical models for medication adherence research; leading the development of the PersonAlyticsPower statistical modeling and power analysis R package for small N, within-subjects, and idiographic clinical trials; and leading a team developing the psa2013 R package for monitoring implementation progress and racial equity of the Public Safety Assessment pretrial risk assessment. In addition, he has methodological expertise in data visualization, multiple/subgroup analysis, latent variable measurement models, longitudinal and survival data analysis, latent variable mixture models, multiple systems estimation, and social network analysis.

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