Skip to main content


Table 1 Characteristics of Efficacy vs. Effectiveness Trial Designs (after [8])

From: An introduction to implementation science for the non-specialist

  Efficacy Trial Effectiveness Trial
Validity Priority Internal > External External ≥ Internal
Population and Sample • Highly selected for condition of interest, narrowly defined • Selected for condition of interest, reflecting presentation in source population
• Few comorbidities • Comorbidities resemble those in population to which results will be applied; only those who cannot practically or ethically participate are excluded
• Willing and motivated participants
Intervention • Intervention staff are highly qualified • Staff selection, training, and fidelity monitoring resemble those likely to be feasible in target sites outside of the protocol proper
• Training may be intensive
• Fidelity monitoring may be similarly intensive
Outcome Measures and Data Collection • Outcome measurements can be extensive, casting a wide net for potential secondary effects, moderators and mediators, or adverse effects • Outcome batteries minimize respondent burden (in terms of both frequency and length of assessments) since subjects are heterogeneous in their willingness and capability to participate
  • Since subjects are motivated, respondent burden less of a concern • Accordingly, outcome measures chosen carefully to target fewer outcomes, and must be simple to complete
Data Analysis • Standard statistical approaches suffice, and data-intensive analyses may be feasible • Analyses to account for greater sample heterogeneity
• Analyses account for more missing data and data not missing at random