Prevention of Alcohol Purchase and Use Among Adolescents Design Two: Staggered Entry of 10 Intervention Sites Harold D. Holder, Ph.D. Senior Scientist, Prevention Research Center, Pacific Institute for Research and Evaluation Berkeley, CA National Institutes of Health May 4-5, 2004

Design 2--Rationale (3) Reaction bias- Communities which are denied intervention can create their own intervention which confounds ability to be controls. (1) Documentation- Requirement of NIH reviewers to have signed agreements of participation creates local awareness and expectation. creates local awareness and expectation. (1) Documentation- Requirement of NIH reviewers to have signed agreements of participation creates local awareness and expectation. creates local awareness and expectation. (2) Ethics- Systematic denial of intervention, based upon selection criteria. (2) Ethics- Systematic denial of intervention, based upon selection criteria.

Design 2: Outline communities with 5 selected for first wave of intervention Communities not included in first wave have delayed initiation, e.g., in pairs Selection for initiation waves can be random or purposeful. Requires parallel outcome measurement Essential to know dates of actual implementation and dosage/strength of implementation in all communities. 5. Enables test of sufficiency of intervention (short term compared to longer term) 6.

Design two T1 T2 T3 T4 T5. … Tn O 1 X O 2 O 3 O 4 O 5 ……….O n O 1 O 2 X O 3 O 4 O 5 O 1 O 2 O 3 X O 4 O 5 O 1 O 2 O 3 O 4 X O

Trade Offs RCT Design 1 Design 2 Assignment (Permits effectiveness trial but requires large candidate pool) Permits trial with fewer cases and enables communities to develop interventions which match their values and norms. Controls (can be biased with mismatched trends) Can control for trending using matching May be difficult to obtain matching controls for trending Ethics (denial of intervention, moderate risk of contamination) Denial of intervention, moderate risk for contamination but less than Design 2 No denial of intervention but increased risk of contamination. Attribution (IF randomization fulfilled and no contamination, then easier to attribute effects) Requires greater complex analyses to increase confidence in attribution of effect.