- report (received feedback reports)
- session (group sessions)
- face-to-face (personal interviews)
An older study on prescribing quality in Spain showed that one-to-one was better than group learning. 
It is likely that local context and the exact mode of delivery of interventions explains a lot of the variation in outcomes. What is hard in this type of research is to learn what can be generalised to other circumstances.
Lopez-Picazo JJ, Ruiz JC, Sanchez JF, Ariza A, Aguilera B. A randomized trial of the effectiveness and efficiency of interventions to reduce potential drug interactions in primary care. Am J Med Qual 2011 Apr;26(2):145-153.[cited 2011 Jul 25] Available from: http://www.ncbi.nlm.nih.gov/pubmed/21403177
Figueiras A, Sastre I, Tato F, Rodríguez C, Lado E, Caamaño F, Gestal-Otero JJ. One-to-one versus group sessions to improve prescription in primary care: a pragmatic randomized controlled trial. Med Care 2001 Feb;39(2):158-167. Available from: http://www.ncbi.nlm.nih.gov/pubmed/11176553