Experimental Designs

In this section, we describe different types of experimental designs that can be used by behavioral intervention scientists to optimize different types of Adaptive Interventions.

  • Sequential Multiple Assignment Randomized Trials (SMARTs) can be used to develop optimized Adaptive Interventions (AIs)
  • Micro-randomized Trials (MRTs) can be used to develop optimized Just-in-Time Adaptive Interventions (JITAIs)
  • Hybrid SMART-MRTs can be used to develop optimized Multimodal Adaptive Interventions (MADIs)
  • Multilevel Implementation SMARTs (MI-SMARTs) can be used to develop optimized Multilevel Adaptive Implementation Strategies (MAISYs)

Sequential, Multiple-Assignment, Randomized Trials

Scientists often have multiple questions, across multiple stages, about how best to construct an AI. Sequential, multiple-assignment, randomized trials (SMART) are a type of experimental design used for developing an optimized Adaptive Intervention (AI). In a SMART, the unit of intervention (e.g., the patient) is randomized at more than one stage. Each stage of intervention corresponds to scientific questions about the selection and adaptation of intervention options (e.g., treatments) at particular points in time.

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Micro-Randomized Trials

Micro-randomized trials (MRTs) are a type of experimental design used to construct an optimized Just-in-Time Adaptive Intervention (JITAI). In MRTs, the unit of intervention (e.g., patient) may be randomized many times (e.g., hundreds or even thousands of times) over the course of a study at points in time when it is plausible that an intervention is needed. MRTs help behavioral intervention scientists answer scientific questions about the dynamic conditions (e.g., internal, environmental) under which it is best to deliver particular intervention options in a JITAI.

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Hybrid SMART-MRTs

Hybrid SMART-MRTs are a type of experimental study design used to construct an optimized Multimodal Adaptive Intervention (MADI). In Hybrid SMART-MRTs, the unit of intervention (e.g., patient), is randomized multiple times across different intervention modalities (e.g., a human-delivered modality and a digital modality). These randomizations help us answer scientific questions about how best to combine services (e.g., treatments) that are sequenced and adapted by different modalities at different time scales.

For example, consider optimizing a MADI that includes a behavioral intervention delivered every 2 weeks by a clinician, coupled with a smartphone (digital) app that is designed to encourage daily engagement in healthy behaviors. A Hybrid SMART-MRT may randomize patients: (i) every two weeks to understand the effect of transitioning to a more intensive behavioral intervention or to stay the course, as well as (ii) every evening to understand the effect of sending a digital prompt to engage in healthy behaviors.

Multilevel Implementation SMARTs

Multilevel Implementation SMARTs (MI-SMART) are a type of experimental study design used to construct an optimized Multilevel Adaptive Implementation Strategy (MAISY). In a MI-SMART, there are multiple levels (e.g., clinic and providers within clinic) and multiple time points of randomization. These randomizations help us answer scientific questions about how best to sequence and adapt different strategies across multiple levels of implementation.

For example, consider optimizing a two-stage MAISY for implementing cognitive behavioral therapy (CBT) at high schools across Michigan, which often have multiple school psychologists (SPs) on staff. A MI-SMART may randomize: (i) schools to understand the effect of a school-wide CBT skills coaching strategy in the first stage, and (ii) SPs within schools to understand the effect of a self-efficacy promotion strategy in the second stage.