Instead of doing a new study, the researchers analyzed information from 81 studies that had compared different approaches for providing preventive services (vaccination and cancer screening). The researchers categorized approaches into seven areas: reminders, education, provider feedback about past performance, financial incentives, regulatory actions, mass media campaigns, and organizational change. Organizational change was defined as changing a health care system to improve performance of preventive services. The researchers then used special statistical analyses (meta-regression) to see which types of approaches were most effective.