Studying interventions is hard work, especially when the interventions do not lend themselves to randomized controlled designs! This is one reason that risk-factor studies greatly outnumber intervention studies in many critical areas, such as disparities in health outcomes, HIV transmission, substance abuse, and violence.

But the pay-off of developing, studying, and translating interventions into practice – changing the world – is tremendous. Early in my career, I published many descriptive and risk-factor studies. They helped me hone my statistical skills and some may have been of help to others in designing interventions. But I am proudest of the work that I have done developing and implementing interventions, so much so that I no longer perform risk-factor studies (although I still help people with theirs, while trying to recruit them to do intervention studies). I hope that this book will recruit you to the world of intervention studies.