Hybrid Experimental Designs

Various hybrid experimental designs are possible, such as hybrids of a standard factorial design with a SMART or an MRT, or a hybrid combining a SMART and an MRT. They are used to study the effects of intervention components which may be delivered and adapted on different timescales—slow (e.g., monthly) and fast (e.g., daily), and to provide information for designing effective Multimodal Adaptive Interventions (MADI).

One example of a MADI would be an intervention which combines coaching sessions and daily prompts from a mobile device, where the intensity of coaching is adapted monthly (e.g., based on progress in treatment) and the delivery of a prompt is adapted daily (e.g., based on daily mood). A SMART-MRT hybrid could provide useful information for answering scientific questions about how to construct such a MADI.

You can learn more about hybrid experimental designs from these papers:

Nahum-Shani, I., Dziak, J. J., Walton, M. A., & Dempsey, W. (2022). Hybrid Experimental Designs for Intervention Development: What, Why, and How. Advances in Methods and Practices in Psychological Science, 5(3): 1-15. Online at https://doi.org/10.1177/25152459221114279.

Nahum-Shani, I., Dziak, J. J., Venera, H., Pfammatter, A. F., Spring, B., & Dempsey, W. (2023). Design of Experiments with Sequential Randomizations on Multiple Timescales: The Hybrid Experimental Design. Preprint on http://arxiv.org/abs/2302.09046.