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Bernal-Delgado E, Galeote-Mayor M, Pradas-Arnal F, Peiro S. Evidence-based educational outreach visits: Effects on prescription of non-steroidal anti-inflammatory drugs. JECH 2002; 56: 653-8. This study provides a model to analyse two of the designs presented and to discuss the threats to internal and external validity present in both.

The study behaves like a pretest-postest design with an equivalent group for the main variable (changes in prescription behaviour), and like a time series composed of equivalent groups for the secondary variable (change is cost per prescription).