  Psychological interventions, especially those leveraging mobile and wireless
technologies, often include multiple components that are delivered and adapted
on multiple timescales (e.g., coaching sessions adapted monthly based on
clinical progress, combined with motivational messages from a mobile device
adapted daily based on the person's daily emotional state). The hybrid
experimental design (HED) is a new experimental approach that enables
researchers to answer scientific questions about the construction of
psychological interventions in which components are delivered and adapted on
different timescales. These designs involve sequential randomizations of study
participants to intervention components, each at an appropriate timescale
(e.g., monthly randomization to different intensities of coaching sessions and
daily randomization to different forms of motivational messages). The goal of
the current manuscript is twofold. The first is to highlight the flexibility of
the HED by conceptualizing this experimental approach as a special form of a
factorial design in which different factors are introduced at multiple
timescales. We also discuss how the structure of the HED can vary depending on
the scientific question(s) motivating the study. The second goal is to explain
how data from various types of HEDs can be analyzed to answer a variety of
scientific questions about the development of multi-component psychological
interventions. For illustration we use a completed HED to inform the
development of a technology-based weight loss intervention that integrates
components that are delivered and adapted on multiple timescales.

Methodology