Table 1 Glossary of terms relevant to rollout designs in implementation research
From: Rollout trial designs in implementation research are often necessary and sometimes preferred
Term | Definition | Examples |
|---|---|---|
Trial Design | A specification of hypotheses and how they are to be addressed rigorously in a comparison of alternatives | Implementation trial that uses a stepped-wedge design to compare implementation as usual to a new implementation strategy |
Condition | A specified state defining a testable hypothesis | New implementation strategy |
Unit | A generic member of a named entity or level in a design | Patient, Clinician, Clinic |
Unit of observation | Level of unit where observation occurs | Program reach measured at patient level; fidelity measured at clinician level |
Unit of assignment | Level of unit where implementation assignment occurs | Clinics assigned to different implementation strategies; counties assigned to different time of implementation |
Assignment | Process or instantiation of assigning units to conditions | Random assignment of clinics to start implementing at different times, Selection of implementation timing by agency leadership |
Cluster | A collection of units sharing one or more attributes | All clients served by the same case manager |
Pre-existing Clusters | Units with an affiliation that predates the design | All clinicians working in the same clinic |
Design-formed Clusters | Units grouped together by the design itself | A learning collaborative formed by having clinics work together to overcome implementation barriers |
Phase | A defined section regarding the course of a specific implementation strategy | A sustainability phase when external supports are withdrawn from an implementation strategy |
Stage | A section of an implementation strategy with clearly defined events for entrance and completion | Engagement stage of the Stages of Implementation Completion |
Implementation Outcome | A measure of the implementation quality, quantity, speed, or duration | Fidelity to the defining or necessary aspects of a program or service |
Cohort | A cluster of those units assigned to start their designated new implementation at same time | All clinics in a stepped-wedge design that start delivering a new implementation strategy at the same time |
Roll-Out or Step | A point in time where an initial assignment of one or more units occurs | A stepped-wedge design with 6 distinct times where one or more units begins implementing a new strategy |
Period | A segment of time where all units’ implementation strategies are held fixed | The time interval between two roll-outs |
Wedge | An upper or lower triangular structure, cross-classified by time periods and cohorts, all sharing the same implementation strategy and same measurement | In a design that begins measuring implementation outcomes when a unit switches to its new implementation strategy, the triangle consisting of time points where this occurs |
Randomized Block Design | Units within the same cluster are assigned randomly to alternative conditions | A wait-listed design where units are first paired to form a block, then assigned randomly to which begins a new implementation strategy first |
Randomized Roll-Out Design | Units are randomly assigned their start times for a new condition | A randomized stepped-wedge implementation trial |
Head-to-Head Implementation Trial | Two conditions are compared by random assignment of conditions within a cohort | A single-wedge roll-out design where each cohort divides units into two starting implementation strategies and begins measuring outcomes then |
Stepped-Wedge Design | All cohorts cross from one condition to another, with measurement of outcomes before and after crossover in each unit | A 2-wedge stepped wedge design where patient-level reach is measured the same way across all time periods and cohorts |